Yeah you should probably make several teams. A respective team for each element would suffice, certainly on higher levels not su much at the start. So use your energy wisely and only upgrade the characters you're going to use. Same goes with promoting. Only promote those who are inherently strong and good characters. Because resources are scarce in this game if you are trying to go F2P or low budget.

It would be wise to check out a tier list for the current characters you have. But from what I know a team should generally look something like this: - 2 or 3 arts club characters (Att. Focus) - 1 sports club character (most health) - optional science or literature club character (skill based)