Spending Exp to get better is a really neat idea. I would also assume that with that, there would be a cost of, say, (Spell Level + 1) x 5 for learning new spells (so that it actually costs something to learn a new cantrip instead of, "I lurn all of da spellzz at once!").

Also, I've seen those Triforce D4s. <3

Rlly tired rn, I'll try to answer better in the morning b4 work.