Route 106 and Granite Cave
Route 106 is fairly barren, with only a few Trainers dotting the sandy beaches. You can fish for a few Pokemon, but they're the same as in Dewford Town and shouldn't be overly exciting. Keep in mind that you can return here after being able to use Surf outside of battle.
Fisherman Ned is the first Trainer you can fight. He uses a Tentacool Lv. 13. To the west of him is Backpacker Graeme and he has a Slakoth Lv. 13, which can only attack every other turn thanks to its Truant ability.
The entrance to Granite Cave is just southwest of Graeme, but you can actually follow the sandy path to the northwest of him along the beach to reach another Fisherman, Fisherman Elliot, who uses a Magikarp Lv. 10 and a Tentacool Lv. 12. There's also a Protein just past him, which you can use to raise your Pokemon's Attack stat permanently just like Super Training, or you can sell it for a respectable 4,900.
Anyway, whenever you're ready, head inside of Granite Cave!
Granite Cave
If you remember the Granite Cave from the old games, it's been drastically simplified, particularly during your early visits here. You no longer need Flash to locate Steven in the cave. Instead, all you need to do is follow the path until you find a Hiker, then head north.
Talk to the Hiker, though, and he'll give you TM70 Flash, a move which lowers the target's Accuracy. It can also light up darker areas to make it easier to navigate. There's a dirt ramp next to him, but you'll need the Mach Bike, accessible later on in Mauville City, before you can scale that and reach other areas of Granite Cave.
Head north, climbing down the stairs and into the next room, where you'll find Steven. He's spending his time looking at the murals in the back of the cave, wondering about Primal Forms and Mega Evolution, and then he'll spot you. You'll give him the Letter and then, after some talking, he'll give you TM71 Steel Wing, a fairly strong Steel-type move that many bird-like Pokemon are capable of learning. It's not too bad of a move to use at this point in the game, plus it gives you some coverage against Fairy-type Pokémon, which is always appreciated.
Now that you've got that out of the way, it's time to head back to Dewford Town. Talk to Mr. Briney and he'll now allow you to set sail for Route 109 near Slateport City!
Fisherman Ned is the first Trainer you can fight. He uses a Tentacool Lv. 13. To the west of him is Backpacker Graeme and he has a Slakoth Lv. 13, which can only attack every other turn thanks to its Truant ability.
The entrance to Granite Cave is just southwest of Graeme, but you can actually follow the sandy path to the northwest of him along the beach to reach another Fisherman, Fisherman Elliot, who uses a Magikarp Lv. 10 and a Tentacool Lv. 12. There's also a Protein just past him, which you can use to raise your Pokemon's Attack stat permanently just like Super Training, or you can sell it for a respectable 4,900.
Anyway, whenever you're ready, head inside of Granite Cave!
Granite Cave
If you remember the Granite Cave from the old games, it's been drastically simplified, particularly during your early visits here. You no longer need Flash to locate Steven in the cave. Instead, all you need to do is follow the path until you find a Hiker, then head north.
Talk to the Hiker, though, and he'll give you TM70 Flash, a move which lowers the target's Accuracy. It can also light up darker areas to make it easier to navigate. There's a dirt ramp next to him, but you'll need the Mach Bike, accessible later on in Mauville City, before you can scale that and reach other areas of Granite Cave.
Head north, climbing down the stairs and into the next room, where you'll find Steven. He's spending his time looking at the murals in the back of the cave, wondering about Primal Forms and Mega Evolution, and then he'll spot you. You'll give him the Letter and then, after some talking, he'll give you TM71 Steel Wing, a fairly strong Steel-type move that many bird-like Pokemon are capable of learning. It's not too bad of a move to use at this point in the game, plus it gives you some coverage against Fairy-type Pokémon, which is always appreciated.
Now that you've got that out of the way, it's time to head back to Dewford Town. Talk to Mr. Briney and he'll now allow you to set sail for Route 109 near Slateport City!
Route 109
In order to get to Route 109, you're first going to need to deliver the Letter to Steven in the Granite Cave, then return to Dewford Town and talk to Mr. Briney, who tells you that you need to deliver the Devon Parts to a man named Captain Stern in Slateport City. He'll offer to take you to the beach of Route 109, just south of Slateport City.
You can fight a Trainer, Sailor Huey, near the dock. He uses a Machop Lv. 15. Northeast of the dock, you can find two Tubers. The girl gives you Soft Sand, which is a held item that increases the power of that Pokemon's Ground-type moves by 20%.
North of her, in the eastern part of the Route, is Tuber Lola. She uses an Azurill Lv. 14, a Normal/Fairy-type. West of her is Sailor Edmond, and he's got a Wingull Lv. 12 and a Machop Lv. 14. South of Edmond is Tuber Ricky and he uses a Zigzagoon Lv. 14.
Anyway, head outside of the Seashore House and then to the north, into Slateport City!
You can fight a Trainer, Sailor Huey, near the dock. He uses a Machop Lv. 15. Northeast of the dock, you can find two Tubers. The girl gives you Soft Sand, which is a held item that increases the power of that Pokemon's Ground-type moves by 20%.
North of her, in the eastern part of the Route, is Tuber Lola. She uses an Azurill Lv. 14, a Normal/Fairy-type. West of her is Sailor Edmond, and he's got a Wingull Lv. 12 and a Machop Lv. 14. South of Edmond is Tuber Ricky and he uses a Zigzagoon Lv. 14.
Anyway, head outside of the Seashore House and then to the north, into Slateport City!
Slateport City
There are two entrances to Slateport City from Route 109, but they really just determine where you start out in the city. Since there's nothing all that interesting near the eastern entrance, I'll just assume that you're taking the western entrance.
In the southwest and west part of Slateport City, you'll find the Slateport Market. Might as well check it out now. There are various shops around the Slateport Market for you to buy things, but not everything is available right away.
The shop with the balloons and the wallpaper for the logo sells various items for your Super-Secret Base, but you'll need TM94 Secret Power in order to buy anything there.
The same goes for the shop just to the west with the heart on it, except it sells various dolls and things. You can't buy anything here just yet. However, there's a super-important item south of the cart with the Marill doll. Pick up the Alakazite Mega Stone, which will eventually allow you to Mega Evolve Alakazam into Mega Alakazam. You need to first have the Mega Bracelet in order to Mega Evolve any Pokémon, though.
The shop with a blue roof and a fist symbol above it has two people outside of it. The man sells you very expensive vitamin items which permanently boost your Pokémon's stats. This includes Protein, Iron, Calcium, Zinc, Carbos, and HP Up, all for 9,800 each. You can accomplish the same result by using Super Training, so don't bother with these for now, as they're way too expensive for this point in the game. The girl next to the guy will determine whether your Pokémon's Effort Values (EVs) are maxed out and will give your Pokémon an Effort Ribbon if they are.
The woman in the shop to the right with the blue roof will sell incense for your Pokémon. These are held items that have beneficial effects, plus, if held by certain Pokémon at the Pokémon Day-Care, they can cause the Pokémon to produce certain "baby" Pokémon, such as Azurill and Wynaut.
Once you exit the Slateport Market from the northern side, you'll find the Pokémon Fan Club. There are a bunch of Pokémon Fans inside, as well as an assortment of cute Pokémon such as Skitty, Zigzagoon, and Marill, which you can scan with your DexNav if you want to add them as "seen" in your Pokédex. You can talk to the Pokémon Breeder in the corner of the room and she'll offer to give any Furfrou you have a trim for 500. Furfrou is native to the Kalos region, not the Hoenn region, so it's not likely you'll have a Furfrou at this point without trading.
Talk to the interviewer in the Fan Club and she'll ask if you'd like to tell her about your lead Pokémon. If you say yes, she'll interview you and you'll get a chance to say a short message about that Pokémon. This message will be displayed over the BuzzNav and on TV sometimes, so keep it appropriate! Talk to the woman up by the portraits and, if your lead Pokémon is at least somewhat friendly towards you, you'll be given a Soothe Bell, which is a held item that increases how quickly the holder's happiness rises. Lastly, the Pokémon Fan Club Chairman will examine your lead Pokémon to examine its contest stats. If they're high enough, he'll reward you with a special Scarf item depending on which stat is high — a Blue Scarf if its Beauty is high, a Green Scarf if its Cleverness is high, a Pink Scarf if its Cuteness is high, a Red Scarf if its Coolness is high, or a Yellow Scarf if its Toughness is high. While held, these increase the respective contest stat by a bit more during the Appeal Round of Pokémon Contest Spectaculars.
The house to the north is the Name Rater's house, and he will allow you to change your Pokémon's nicknames. Just keep in mind that you can only change the nicknames of Pokémon you've caught yourself; traded Pokémon or Pokémon that have an OT and ID No. different from your own can't be renamed.
South and then to the west of the Poké Mart is the Oceanic Museum with a large line of either Team Aqua or Team Magma Grunts, depending on your version, unless you've already visited the Shipyard. You won't be able progress until you've visited the Shipyard.
In the very southeast corner of Slateport City, you'll find the Shipyard, which is where you'll need to make sure you visit. Inside, you'll meet Dock, who will inform you that you need to deliver the Devon Parts to Captain Stern in the Oceanic Museum.
Now that you've visited the Shipyard, head back to the Oceanic Museum, which is just to the north of the Shipyard. The line of grunts has cleared out now, leaving you free to enter.
You'll have to pay 50 to enter the museum. If you don't have that much money, don't worry, you'll be "with the group that came in earlier" and can get in for free, but 50 isn't much at all.
There are a whole bunch of Team Aqua or Team Magma Grunts inside of the museum. Talk to the one in the bottom-right corner of the first floor and he'll give you TM46 Thief, a 60 power Physical-based Dark-type move that also steals the foe's held item when used in battle, giving it to the user so long as it isn't already holding an item. If used against wild Pokémon, you even get to keep the item, so it's very useful to steal useful items from wild Pokémon — you don't permanently get to keep items held by Trainers' Pokémon, though. Even if you don't use it for stealing items, it's still a solid 60 power Dark-type move to help improve your type coverage, plus a lot of different Pokémon can learn it, even ones that aren't Dark-type.
Head upstairs and then to the bottom-right corner of the room. Captain Stern is there examining a model of a ship, and when you talk to him, two Team Aqua (Alpha Sapphire) or Team Magma (Omega Ruby) Grunts will show up, introduce themselves as Team Aqua or Magma, demand you hand over the Devon Parts, and then fight against you.
In Omega Ruby, the first Team Magma Grunt uses a Numel Lv. 16 and the second Team Magma Grunt uses a Zubat Lv. 14 and a Numel Lv. 14.
In Alpha Sapphire, the first Team Aqua Grunt uses a Carvanha Lv. 16♂ and the second Team Aqua Grunt uses a Zubat Lv. 14 and a Carvanha Lv. 14.
After beating the two Grunts, the Boss of either Team Aqua or Team Magma will walk into the room, based on which game you're playing. The leader of Team Aqua introduces himself as Archie while the leader of Team Magma introduces himself as Maxie.
Either Archie or Maxie will talk about their plans and ambitions for their team for awhile, and, after plenty of dialogue, will leave you and Captain Stern be. You'll give Captain Stern the Devon Parts afterwards and then he'll head off.
Go on and leave the Oceanic Museum, heal up your Pokémon if necessary, and then head north towards the entrance to Route 110. As you do so, you'll overhear two people talking about Lisia and Ali, and they then run off towards the Contest Spectacular Hall.
You'll be forced to watch the commotion, which is all because of a girl named Lisia and her Altaria, Ali. She's scouting for a new Trainer to participate in Contest Spectaculars and, naturally, she'll choose you for the role. She'll give you the Contest Pass, which is required in order to enter contests, and the Pokéblock Kit, which allows you to make Pokéblocks using your berries.
Now that you have these things, you can enter a Pokémon Contest Spectacular anywhere that you see one of those Contest Hall buildings. These are similar to the old Pokémon Contests in Ruby, Sapphire, and Emerald, where you increase different qualities of your Pokémon, such as their Coolness, Beauty, and so on, by using Pokéblocks on them. You can make Pokéblocks by putting different berries inside of the Pokéblock Kit — don't worry, if you remember the old Berry Blender from the older games, that process is gone, as now you just select the berries you want to blend into a Pokéblock and it blends them very well, no minigame necessary.
Contests are totally optional, but they can be pretty fun as well. While a thorough section on the Contest Spectaculars will be added later on, you should definitely stop by the Contest Hall and participate in a contest. Enter just one contest and, even if you lose (if you lose, you'll be given a Lum Berry, so it's actually fine to lose!), you'll be given a special level 20 Cosplay Pikachu after participating. Cosplay Pikachu can change its appearance by returning to the break room and talking to the Pokémon Breeder that gives you the Cosplay Pikachu. It has an exclusive move depending on which costume its wearing. It also has excellent contest stats from the get-go.
Anyway, whether you want to invest time in contests or not is totally your call, but whenever you're ready to proceed further in the game, head north onto Route 110!
In the southwest and west part of Slateport City, you'll find the Slateport Market. Might as well check it out now. There are various shops around the Slateport Market for you to buy things, but not everything is available right away.
The shop with the balloons and the wallpaper for the logo sells various items for your Super-Secret Base, but you'll need TM94 Secret Power in order to buy anything there.
The same goes for the shop just to the west with the heart on it, except it sells various dolls and things. You can't buy anything here just yet. However, there's a super-important item south of the cart with the Marill doll. Pick up the Alakazite Mega Stone, which will eventually allow you to Mega Evolve Alakazam into Mega Alakazam. You need to first have the Mega Bracelet in order to Mega Evolve any Pokémon, though.
The shop with a blue roof and a fist symbol above it has two people outside of it. The man sells you very expensive vitamin items which permanently boost your Pokémon's stats. This includes Protein, Iron, Calcium, Zinc, Carbos, and HP Up, all for 9,800 each. You can accomplish the same result by using Super Training, so don't bother with these for now, as they're way too expensive for this point in the game. The girl next to the guy will determine whether your Pokémon's Effort Values (EVs) are maxed out and will give your Pokémon an Effort Ribbon if they are.
The woman in the shop to the right with the blue roof will sell incense for your Pokémon. These are held items that have beneficial effects, plus, if held by certain Pokémon at the Pokémon Day-Care, they can cause the Pokémon to produce certain "baby" Pokémon, such as Azurill and Wynaut.
Once you exit the Slateport Market from the northern side, you'll find the Pokémon Fan Club. There are a bunch of Pokémon Fans inside, as well as an assortment of cute Pokémon such as Skitty, Zigzagoon, and Marill, which you can scan with your DexNav if you want to add them as "seen" in your Pokédex. You can talk to the Pokémon Breeder in the corner of the room and she'll offer to give any Furfrou you have a trim for 500. Furfrou is native to the Kalos region, not the Hoenn region, so it's not likely you'll have a Furfrou at this point without trading.
Talk to the interviewer in the Fan Club and she'll ask if you'd like to tell her about your lead Pokémon. If you say yes, she'll interview you and you'll get a chance to say a short message about that Pokémon. This message will be displayed over the BuzzNav and on TV sometimes, so keep it appropriate! Talk to the woman up by the portraits and, if your lead Pokémon is at least somewhat friendly towards you, you'll be given a Soothe Bell, which is a held item that increases how quickly the holder's happiness rises. Lastly, the Pokémon Fan Club Chairman will examine your lead Pokémon to examine its contest stats. If they're high enough, he'll reward you with a special Scarf item depending on which stat is high — a Blue Scarf if its Beauty is high, a Green Scarf if its Cleverness is high, a Pink Scarf if its Cuteness is high, a Red Scarf if its Coolness is high, or a Yellow Scarf if its Toughness is high. While held, these increase the respective contest stat by a bit more during the Appeal Round of Pokémon Contest Spectaculars.
The house to the north is the Name Rater's house, and he will allow you to change your Pokémon's nicknames. Just keep in mind that you can only change the nicknames of Pokémon you've caught yourself; traded Pokémon or Pokémon that have an OT and ID No. different from your own can't be renamed.
South and then to the west of the Poké Mart is the Oceanic Museum with a large line of either Team Aqua or Team Magma Grunts, depending on your version, unless you've already visited the Shipyard. You won't be able progress until you've visited the Shipyard.
In the very southeast corner of Slateport City, you'll find the Shipyard, which is where you'll need to make sure you visit. Inside, you'll meet Dock, who will inform you that you need to deliver the Devon Parts to Captain Stern in the Oceanic Museum.
Now that you've visited the Shipyard, head back to the Oceanic Museum, which is just to the north of the Shipyard. The line of grunts has cleared out now, leaving you free to enter.
You'll have to pay 50 to enter the museum. If you don't have that much money, don't worry, you'll be "with the group that came in earlier" and can get in for free, but 50 isn't much at all.
There are a whole bunch of Team Aqua or Team Magma Grunts inside of the museum. Talk to the one in the bottom-right corner of the first floor and he'll give you TM46 Thief, a 60 power Physical-based Dark-type move that also steals the foe's held item when used in battle, giving it to the user so long as it isn't already holding an item. If used against wild Pokémon, you even get to keep the item, so it's very useful to steal useful items from wild Pokémon — you don't permanently get to keep items held by Trainers' Pokémon, though. Even if you don't use it for stealing items, it's still a solid 60 power Dark-type move to help improve your type coverage, plus a lot of different Pokémon can learn it, even ones that aren't Dark-type.
Head upstairs and then to the bottom-right corner of the room. Captain Stern is there examining a model of a ship, and when you talk to him, two Team Aqua (Alpha Sapphire) or Team Magma (Omega Ruby) Grunts will show up, introduce themselves as Team Aqua or Magma, demand you hand over the Devon Parts, and then fight against you.
In Omega Ruby, the first Team Magma Grunt uses a Numel Lv. 16 and the second Team Magma Grunt uses a Zubat Lv. 14 and a Numel Lv. 14.
In Alpha Sapphire, the first Team Aqua Grunt uses a Carvanha Lv. 16♂ and the second Team Aqua Grunt uses a Zubat Lv. 14 and a Carvanha Lv. 14.
After beating the two Grunts, the Boss of either Team Aqua or Team Magma will walk into the room, based on which game you're playing. The leader of Team Aqua introduces himself as Archie while the leader of Team Magma introduces himself as Maxie.
Either Archie or Maxie will talk about their plans and ambitions for their team for awhile, and, after plenty of dialogue, will leave you and Captain Stern be. You'll give Captain Stern the Devon Parts afterwards and then he'll head off.
Go on and leave the Oceanic Museum, heal up your Pokémon if necessary, and then head north towards the entrance to Route 110. As you do so, you'll overhear two people talking about Lisia and Ali, and they then run off towards the Contest Spectacular Hall.
You'll be forced to watch the commotion, which is all because of a girl named Lisia and her Altaria, Ali. She's scouting for a new Trainer to participate in Contest Spectaculars and, naturally, she'll choose you for the role. She'll give you the Contest Pass, which is required in order to enter contests, and the Pokéblock Kit, which allows you to make Pokéblocks using your berries.
Now that you have these things, you can enter a Pokémon Contest Spectacular anywhere that you see one of those Contest Hall buildings. These are similar to the old Pokémon Contests in Ruby, Sapphire, and Emerald, where you increase different qualities of your Pokémon, such as their Coolness, Beauty, and so on, by using Pokéblocks on them. You can make Pokéblocks by putting different berries inside of the Pokéblock Kit — don't worry, if you remember the old Berry Blender from the older games, that process is gone, as now you just select the berries you want to blend into a Pokéblock and it blends them very well, no minigame necessary.
Contests are totally optional, but they can be pretty fun as well. While a thorough section on the Contest Spectaculars will be added later on, you should definitely stop by the Contest Hall and participate in a contest. Enter just one contest and, even if you lose (if you lose, you'll be given a Lum Berry, so it's actually fine to lose!), you'll be given a special level 20 Cosplay Pikachu after participating. Cosplay Pikachu can change its appearance by returning to the break room and talking to the Pokémon Breeder that gives you the Cosplay Pikachu. It has an exclusive move depending on which costume its wearing. It also has excellent contest stats from the get-go.
Anyway, whether you want to invest time in contests or not is totally your call, but whenever you're ready to proceed further in the game, head north onto Route 110!