Before going and buying a gun that may or may not work for you - shoot your pump for a bit, and while at the local club see if you can borrow as many different types and makes as you can and see how they work for you. When (if) you find the brand and model that works, then buy one. As BigJim mentioned, a good target grade O/U like one of the B guns is going to run about $2500 and up for new, a little less for used. Some of their field versions can be had for less, but they tend to weigh less as they are designed for more carrying than shooting. In a target gun, weight is your friend, as are typically longer barrels for improved swing dynamics.
Even new semis are getting up there in price, but good used ones from Remington and Beretta can be found for under $1,000.
Buy the fit, not the name. Buy quality so you will have something that lasts and isn't always in the shop. If you truly get into clay target shooting, the cost of the gun will be the cheapest over the long run, so buy quality first. Targets and ammo will cost you more.
Have fun!