For a beginner? The cheapest bucket you can find from a reliable company (Petzl, BD, Camp, Edelrid, etc.). No need to spend the big bucks on some fancy, carbon fiber, ultra comfortable double-deluxe piece until you start caring a lot about weight/comfortability.
This may sound overly-simple, but I suggest "the one that fits". Every helmet fits a bit differently, so go to your local gear shop and try some on and see what you like. If it's a climbing helmet and it fits, then it's the right one for you!
I once found a brand new edelrid shield helmet (in box) for ten dollars at a thrift store. I like that helmet a lot. Not ultralight, but sturdy and fits well.