Focused Prayer and Tainted Oracle should take care of a lot of that. Don't attack with your staff unless you need to or you can kill something. Priests are nearly unstoppable in the late game which...

Yeah but that's for any deck. That comes along with experience. If he likes the Priest Class, than if he sticks with it he can master it and become super proficient with it while still learning how...

Why? He can learn priest off the top.