Pokemon Emerald: Team Help?

I would go with Torchic first for starters. It evolves into the powerful Blaziken. Mudkip works pretty well too. Blaziken is a Fire/Fighting duel type, it'll work well against most of your opponents like the first few gyms, after that you should get an electric type like a Pikachu in the Safari zone to make up for its flying type weakness. If you choose Mudkip/Swampert, get a fire type that will be able to scorch away those nasty grass types that'd do heavy damage to your Swampert.