Magic skill should be earned by defeating a wizard boss for a quest
Mana bar needs to be increased by 5 by level up
In other words, you need a staff for using proper magic, bare hands would make it weaker and a chance to backfire
To prevent spamming a magic skill, it needs to recharge for it depends on how strong it is
I would say fire, health, water, lightning, darkness, shield, and any other kind of magic would change during leveling up
Leveling up for magic influences attacking enemies, using it on yourself, and by gaining books
Exp for magic should need to take a little long since it can be overpowered in some occasions