If I use Evosoda to evolve my Basic Pokemon into a Stage 1, can I then use Wally to further evolve it into a Stage 2 on that same turn.

Yes, but be careful of the order in which you play the cards. Wally says you can use it on a Pokemon that was put into play this turn, but Evosoda says you cannot use it on a Pokemon that was put into play this turn. So you can play Evosoda first then Wally, but you cannot play Wally then Evosoda (on the same Pokemon, of course).

Relevant cards