Skills are what matters most. U can only increase your stats 3 times by doing the jog/study etc.
Get invisibility, mana shield, summon skeleton, demon, rat talismans, drain mana. In the buff screen, cast invisibility on yourself and summon everything you can. In battle, simply heal yourself and don't attack. The fairies won't be able to attack you and will waste mana on summons. Then finish them off.