For in-game, almost anything will do with the exception of blatantly retarded movesets made from liquid fecal matter - I don't think I need to explain what those movesets consist of. However, I will say regardless of Nature, focus on Physical attacks and ditch the Special attacks. Added up, you're losing 10% of your Attack from your Timid Nature, and gaining 100% of it from your Ability. This, essentially means:
100% - 10% from Nature = 90%
90% x 2 due to Ability = 180% Attack
The numbers are definitely in favour of physical attacks.
In any case, since it's in-game, I won't go into much detail since I don't need to. One thing of note though is that upon evolving into Medicham, the Elemental Punches are available to you if you get some Heart Scales and take them to the move relearner in Pastoria.
That should be all there is to it.