Pokémon Ruby and Sapphire/Route 110

Route 110 is a route between Slateport City and Mauville City, there are seven different kinds of wild Pokémon that live here: Electrike, Gulpin, Minun, Poochyena, Oddish, Plusle, and Wingull. Although you can get through this route faster using Cycling Road, you can't take it yet. You will have to go the long way.

Right up ahead, is a house. Inside there's a man hiding under the table. When you have found him, he will ask for a battle, but you don't have to. Go east, under the Cycling Road, and continue north. You will meet your rival halfway there. When you have beaten him/her, you can continue up against Mauville. There are some trainers there, so just go nuts and gather experience.