Googleing the information like Bopp is suggesting is a good idea. It's how I figured out what ultimate's I will get. But if you want more direct details from players themselves, you would need to give us a bit more information about your sprites and your play style.

But for starters, this is what I am planning for each sprite.

Maskeraith: Vengeful Quills, Deadly Shadow Cloak, Chaotic Haze. Shaderon will be used for playing "cryptic assassin" with my enemies.

Drakon: Concussive Firebolt, Backfire Barrier, Frenzied Firestorm. Firestock will serve as a party player to support me and teammates with offense.

Seraphynx: Disintegration Ray, Iron Heart Attack, Seraphic Aura. Phlashlite will be a team shield basically. And some minor combat support.

Well, this is what I'm going for. You may choose differently but I feel this is best for me.