So where is ryze from?

Rune prison.

I could imagine him being from the vodoo lands,but thats simply because it is the only place that is known for its magic.

Otherwise I'd say he could be from noxus,I mean yes he isn't the guy who runs around talking about strenght,but ryze is quite muscular for a mage(and can build quite tanky),which might have come from the noxian way of seeing strenght as the greatest thing ever.

In the headcannon of a friend of mine, Ryze hails from Demacia as a farm laborer, as his headcannon originates pre-Shurima like Ryze's original lore. This is mostly because

1. Noxus seems to be heavily racist, and
2. the implication that Ryze was chased out of colleges for not following rules to the T, which seems to be a very Demacia-esque sort of philosophy.

Why a farm-hand? The appreciation for nature, the natural-cycle of things, a driven ambition to better himself, and the acknowledged importance of staying "in-shape."

Yes.

Not totally sure where he's from originally, but he's currently a resident at the Institute of War. He has a study there, studying ancient magic.