Play Through the Custom Episode Bonus Battles

I mentioned the importance of what-if battles earlier, and Dragon Ball: Sparking Zero takes it a step further with Custom Episodes. These allow players to create their own stories with simple dialogue cutscenes and special rules for battles.
There are also a bunch of developer-made Bonus Battles, and quite a few of them will unlock more characters. Do these to unlock the likes of Caulifa, Future Gohan, and Gogeta (Super). That last one’s especially important if you didn’t pre-order (good for you), and get early unlocks for the character.