Rem 870 is a great gun, no doubt.
However, if you are just getting into skeet, you don't want a pump, trust me.
An autoloader or over-under or side-by-side is definately the way to go.
You just won't have time to cycle it for the second shot.
Granted, really good shooters can and do shoot pumps for skeet from time to time, but they have years of experience, and are skilled at the sport.
For beginners like you and me, we'll find it much less frustrating not to have to worry about cycling the gun as you try to line up your second bird.