Oh boy!!1 If you are going to get involved with Skeet, or any of the clay target games, you will not be satisfied with a cheapie gun.
Do NOT buy a Mossberg or Rem 870. Not suited to Skeet no matter what others say. You will be disadvantaged and will end up spending more in short order.
What does the Beretta give you? In short it is a reliable gun that will go bang when you ask it to. It is an O/U and as such has fewer moving parts. Reliability IS important, and the 686 is reliable. Skeet shooters go through a LOT of ammo.
Skeet requires two shots in quick succession, a pump will slow you down, not to mention jam when you least expect it to.
If you get serious about Skeet you will quickly learn you need four guns to compete, thats right FOUR guns! 12,20,28 and 410. Competition skeet is shot in four gauges. An O/U allows you to buy sub gauge tubes to shoot all four gauges with one gun.
$1500 for the Beretta is a good price for the quality you get. Look around for a used gun, you might find one for less than new. Don't forget a new gun is no longer new after the first round of skeet.
My first clays gun cost $1100, it was an O/U and I dumped it after three years as it was not reliable. It was a Remington BTW. Not all O/U's are well made.
Stick with Beretta or Browning (O/U's) for your first gun. You will not be sorry.
Others will tell you to buy an Auto, they have their fans so I will leave the kudos to them. I prefer O/U's