Greetings aTm papi, and welcome aboard.
If I'm correct, your new gun came with two barrels, and it's the short one that has been drilled for the rear sight. For clay targets your best bet is the long field barrel. It came with a simple bead front sight. If you're thinking of adding any sights, may I suggest that you start with a mid-rib bead on the long barrel. This will essentially make it a target barrel.
As oncounceload mentioned, your eyes are the rear sights. With a target barrel, the purpose of the mid rib bead is to give you consistency in mounting the gun. With the gun properly mounted, the two beads should form a figure. Every-time you mount, you should see the sights make a vertical figure 8. After you're totally acclimated to your new gun, the figure 8 will happen automatically. Then, you'll only use it as a reference point. Say you put on a heavy jacket and something doesn't feel right, then a check for the figure 8 will tell if you're mounted high, low, canted, or correctly. For breaking clay targets, adding a simple mid rib bead is by far the "biggest bang for your buck" modification available. Virtually every comp clay shooter has a two bead set up -- it's very simple and it's very effective.
While shooting clay targets, don't look at the beads, keep your eyes on the target! Once you verify the mount is correct, by seeing the figure 8, then switch your focus to the target distance and keep it there. This is the problem with high visibility sights for clays, they have you focusing at the end of the gun instead of the target. Generally the simple beads work best; however, if you have serious vision problems, and can't make out the figure 8, then you might wanna think about something different.
