I want to learn more about Cassie, can you tell me in which books she have more appearances?  
 
I dont mean the issues numbers (92 in Titans, 61 in WW...), I mean the most apparences at all (not only 1 page in a book...). 
 

A lot of her early appearances were in Young Justice, but the bulk of her appearance have been in the current Teen Titans volume. Right now, she is the leader of the team, and even before that she was usually one of the main three characters in the book.

She's been almost a constant member of the vol. 3 of the Teen Titans and thats reaching issue 93 next month, but the first few issues are probably the best explaining.

start with Young Justice it's such a good read through the entire series then go to Teen Titans vol. 3

I wouldn't say it was a LOT but sure she punched some stuff

to really appreciate the character you will need to brush up on some Young Justice and then follow up with early issues of Teen Titans vol 3 (?)

I think it's probably in the pre-flashpoint teen titans.

In the new 52 cassie is in the first issue of teen titans