*sigh* Another one of these threads, where is it coming out now?
Chimchar is a good starter as he can get past the first few gyms quite easily (Well the first one depends if you evolved him or not :P)
Torterra makes a good tank pokemon, that can beat most if not all gyms, except of course Candice and her Ice powers making Torterra cry
I personally chose Empoleon (Piplup) due to the insane amount of resistances he has, plus with the moveset I gave him, he can sweep rather effectively (in game, competitive is another story)