I listed different strengths and how they effected the powers. We won't have a "leveling up" system exactly, though from time to time I may give characters extra strength or skill points after they used their abilities a lot.
What I mean by levels is the class and strength of your powers.  For example, if I made a Jean Grey style character I'd be a class 3 telekinetic and class two telepath.  The strength for TK would be 7 or eight, and the strength for the TP would be 2 or three, totaling 10.