For deer hunting- Knowledge helps alot, knowing how to set up, etc. But equipment wise, I think #2 would be the scope. Now this does not mean it has to be a $1,000 Swarovski or Zeiss, but just a quality scope such as Nikon, Pentax, Leupold, etc. Something you have confidence in. However, if you are taking for granted you already have a good scope, next I would say ammo. If you get some s**ty ammo then the deer simply ain't going to fall. I would stick with Hornady, or Federal (I shoot Federal, personal preferance) (I don't have experience with Winchester.......sry)

Good Hunting and Straight Shooting