GWS Formosa is a good flyer and it is inexpensive. I would not take it as a first aileron plane, though. It is also a bit small, which might be either good or bad, depending on your circumstances. Formosa 2 is bigger but I have no experience with it.

I trained on a GWS E-Starter which is a forgiving aileron trainer but its aerobatic capabilities in stock form are a bit limited. Removing the dihedral (cut, align, glue, reinforce) and adding power might make it more aerobatic.