Pretty simple and pretty easy as long as you tackle it early on in the game. If you biff it and mess up when you're going along story mode, know that it's typically easier to go back to the Park and just battle someone easy until the achievement dings.
The battles aren't always based off of skill, so make sure that whatever Bakugan you are using is G-pumped to a level you feel comfortable at. The higher you start, the less work you have to worry about putting out.