I didn't use any summons at all, I just summoned them to see their special and that's all...

But let's see...
I used Vaan, Basch and Ashe.

Vaan- Belias, Hasmal, Chaos, and the holy guy
Ashe- Ultima, SHemhazzi, the thunder wind guy in the underground place, Mateus, and another female one... forgot the name...
Bache, only really tried Zodiark with him, though I gave him the fat bio guy, and a few others.