Simple and easy to clean will be the revolver. I'm not sure about recoil, but I think the GP100 is pretty big and heavy, and therefore should have less recoil.
Call your local Wal-Mart to get prices on boxes of Ammo. I can't recall off-hand which is cheaper.
From what you describe, I think you'll be happier with the revolver for your first gun.
Wait six months, then get the semi-auto.