here. Basically, they're timed mini-quests you can run to earn ingredients which can be traded for gear. The better you do completing Challenge objectives, the more ingredients you earn per run. F2Pers need Challenge tokens in order to access them.
INT doesn't boost your dmg directly; instead it boosts your DCs. The harder it is for your spells to be resisted, the more likely they are to do full dmg; or in the case of CC & instakill spells (which tend to be all-or-nothing), take full effect. So maxing out your INT is an important part of building up your wizard. But as stated, Fox's Cunning is temporary and doesn't stack with gear; you also won't gain SPs from temporary buffs, since they wear off when resting.Also to people recommending spells why wouldn't you take fox cunning? Does int not boost spell damage? What does int do then?
Fortunately, as a wizard you can use wands for most stats until you acquire better gear; that way you don't have to waste spell slots on Fox's Cunning, Bear's Endurance, etc.