Whats the best way to level up my summoning in kingdom hearts 2?

im sick of this ive got 7 valor wisdom master and final and i want the paradox cups i dont know how to level up my summon fast and im getting irritated... i looked at some other peoples questions and people said to just kill stuff with the summon up and itll get u 1xp per kill and that was rong... i killed like 200 heartless in the beggining of the world that never was and got like 10 xp.... someone help me!