General

HP.. because it determines your survivability.. you still need to have HP to tank hits with MG

also when MG is dispelled.. you would die from everything if you had Auto MP instead of HP

Mp, because mages can hardly take a hit from monsters without MG, so mp is more important. Plus, they're ginger ales, it'll heal your hp too.

Perma Auto MP is the way to go for most Mages. Your health bar is basically your MP bar (sort of). I've only tried Ginger Ales with the Auto HP but it does heal both. Same goes for Elixirs and Power Elixirs.

I think MP since you get Magic Guard.