Pans warp because of the way they are handled during cooking. Or, more likely, AFTER cooking. Give your pans time to warm up (warm, not hot) before putting the oil in, and don't let them overheat. When cooling, don't COOL them too fast, like by dumping them hot into a sink full of cold water. Let them cool off first.

Otherwise, thicker metal is better than thin. Cheaper pans sometimes use cheaper alloys, but I haven't seen any REALLY cheap stuff around in a long time. Then again, I don't go looking, either. Carbon steel, seasoned and kept oiled are a good option. But they are also easy to warp from mis-handling. Hardened aluminum is more durable that way, but less popular these days because of the aluminum/dementia scare (back in the 90's, IIRC?).

Also, these days, you'll want to get something that will work with induction. If you're not using it now, you will very likely be using it in the future.

Oh - and btw - you can season s/s and carbon steel the same way you do cast iron, with the same non-stick results when done properly. They won't be shiny, but the eggs come out better!