Difference between Foundation 1 and Foundation 2?

I'm curious what the difference is between foundation 1 and foundation 2. Do they build on one another? As a current gymnast, how do I know what level I'm on before I buy the books? 

 

I'm most interested in the Manna component of the foundation series actually. I have a pretty decent manna split hold and solid V. 

F2 follows F1. My recommendation would be to buy F1 and then test yourself for mastery on all the elements; if you find that you're advanced enough for F2, you can just return F1 for a refund.