Honestly, I only shoot o/u shotguns hunting. If I were to get real serious about shooting trap or sporting clays, I would have to think very hard about buying one of these newer recoil mitigating auto's. They would help with 2nd target acquisition on the set ups with 2 birds. I do think those shotguns are pricey, though. Maybe $2000+ I think. I don't trade shotguns much so am not sure. Also, if you really want to get good with a shotgun, you have to have it fit to you. Stocks will have to be modified to fit you. All of my shotguns have been trimmed on LOP because of my awesome TRex arms.
That isn't to say you can't learn to shoot any shotgun well. The main ingredient to successful skeet shooting is pulling the trigger. Thousands. Of. Times.
Technique is important but shooting is a perishable skill. If you don't practice, you suck. At my peak, I would limit out, 15, on dove on less than a box of shells. Pheasants was 5 shells and 3 birds. Now I don't hit 1 in 10 shots because I only shoot 20 rounds a year with drought and babies.
All that being said, I love o/u shotguns and think any of the name brand firearms with solid warranties are going to be plenty high quality. I have 3 Citori's and a Weatherby. Weatherby is fancier and I shoot it worse than my brownings. I really loved a beretta onyx I had years ago but traded it for a shotgun to give my brother.
Buy what you can afford, new or used, with available extra barrel sets that you might want and take it to an expert to have it fit to you. When you get it back after maybe $150 worth of mods, it will shoot so much better you won't believe it.