When you arrive in Dewford, feel free to go west and peruse the Pokémon Center. From there, you can go southeast and probably do the Pokémon Gym, though it’s not really advised for the moment. You can speak with the Fisherman to the east of the Gym, though, to earn an Old Rod .
Walk along the shoreline east of here onto Route 107 briefly to find a Super Repel , then return to town. In the house northeast of the Pokémon Center, you’ll be able to grab a Silk Scarf , too, a hold item that boosts the holder’s Normal moves power by 20%.
There should also be a man in the house north of the Pokemon Center giving out TM36 (Sludge Bomb), which is a good Poison move. Aside from these things, just head north onto Route 106 .