Black and White are my favourite Pokémon games in the franchise.I'll give you the advice my daughter typically gives me. The best team for any Pokemon game is the team you want to play. I'll add that I don't typically go for mono-type teams, particularly in earlier Pokemon games. It's easier to swing monotype teams in the later games since they've added so many dual type Pokemon as they went along.
I will say this, there's a lot of water types in Gen 3, so you're probably going to want a grass type.