If you are new to O/U shotguns - you need to do a little research on O/U's in general / visit some gun stores, talk to your buddies, etc.
In the Browning Citori lineup there are about 25 different models. Their entry level field gun - is the Lightning series - and lists for $ 1,869 but sells new for around $ 1,750.
http://www.browning.com/products/ca...type_id=461&content=citori-lightning-firearms
The Browning Citori Lightning model has been sold for about 35 years. Some of the older versions, sold in the late 1980's are still very good guns ( I bought one new in 1988 for about $ 750 - and still have it) ...and I've since picked up a couple used ones on the market for under $ 1,000. The older screw in choke system was called the Invector / the newer one's since about 1998 are called Invector Plus - but either system is just fine. Prior to 1980 or so / they were fixed chokes / not screw in changeable chokes and I would stay away from those older guns because without changeable chokes the guns are not as versatile.
Today, a Lightning that sold new in 1988 for $ 750 - in very good shape can command at least $ 1,250 on the used market if it has screw in chokes. But I've found a few with scratched up stocks / that I've been able to restore with some time and elbow grease that are fine guns.
There are a lot of inexpensive O/U's on the market Baikal, Stoeger, Mossberg, Remington, TriStar (sold by Cabela's) ....and we debate the pros and cons of those guns on this forum all the time ...but I say stay away from them on the used market / because often they were guns with issues that were sold or traded for something else and no way to know what the issue was ( bad trigger, barrels not hitting the same point of impact, etc ). If you're going to buy one of them / then go with a new one - maybe like the TriStar that sells for around $ 600 new and comes with a 5 yr warranty. None of those guns, in my opinion, are 1/10th as good as a used Browning Citori or Beretta ....but that's my opinion ...but some shooters report they've had good luck with them.
Personally, my bird hunting O/U's are the same guns I shoot Skeet and Sporting Clays with - Browning Citori, XS Skeet model, with adj combs ...but those are out of your budget range - even used they're around $ 2,000.
Good luck / have fun with your search.
I'm not endorsing TriStar shotguns ....just telling you what I know about them - and on their website ....you can see prices, details on their 5 yr warranty, etc ...and Cabela's and others are selling them last I knew. They may or may not be a serviceable shotgun for 5,000 or 10,000 shells - I can't tell you / but I doubt they'll hold much value on the used market. One of my local shops that buys and sells a lot of used guns / says he won't take any more in for trades or buy anymore of them used.
http://www.tristarsportingarms.com/
Apparently their service center is near Kansas City ...