I learned every ability with everyone except Gau, have like 20% of him left and i probably won't finish that, it's definetly a waste of time.

For me VII was the only game worth mastering fully, although i've mastered I,V,VIII (without the pocket station though) and IX (without Excalibur II).
IV DS,VI and IX 100% mastery is insane and i don't call X,X-2 and XII insane.