You can't go wrong with a used 870.
I just went through this same situation...
I looked for used but ended up buying a Beretta 390 at Wally and it shoots great!
LAX is selling his used 11-87 if you want to PM him.
For a NOOB shooting skeet with a pump gives you a disadvantage on the second shot b/c you lose the target racking the second round. I'd stick with a semi or if you have the cash get an o/u.
I stayed away from the 1100 b/c it cannot shoot 3" rounds and I wanted my shottie to be versatile.
Check out shotgun world they have lots of used shotties...