I'm not exactly an expert here, but I'm happy to tell you what I've been using (I'm about to go for my 8th badge).
I've got a
and
.
I grabbed the Bulbasaur off GTS when I got to Golden Rod, cause, as discussed in another thread, there are only so many grass options in HGSS it seems. I'm probably going to sub the Sandshrew for a Gligar when I get access to my little sister's DS in a week or so too, and I'm thinking about adding a Ralts on somewhere.
I think it's really about making the team you choose work for you, in game at least. It's when you start battling human opponents that things get really tough. You're all a crazy bunch of stat-crazed poke-addicts.