you can talk to the guy who sells the cards, and he'll tell you what your score is. as far as levels in creatures, there are none that I'm aware of; I think it's actually that your character isn't high enough level yet (I know, your character level shouldn't matter, but it won't be long 'till you can use it so I wouldn't worry about it)- by fourth level you should be able to use all your creature cards.
