Buy the Rem 870 combo, they are cheap enough and reliable. Don't bother with all the uber remakes from Vang and others, wasted money. Buy several boxes of shells and go shoot.
Buy more shells and keep shooting till you are familiar with the gun, than shoot some more.
Don't waste money on mag extensions, sidesaddles, tactical stocks, attached lights, porting etc.
Buy shells and shoot. OK you may want to take a lesson in Skeet or Trap or Sporting, often worth it to learn proper technique. But the best investment in shotguns is more shells and more shooting.
Forget the Mossbergs, they are problems. You won't find them at money shoots because they just don't work properly. Whenever I have taken a new shooter out on the clays course and they show up with a Mossberg I know I am in for a long afternoon, and they usually end up shooting my gun.
My bloviated opinion as usual