I typically use an 8” gong at 500 hung beside a 66% IPSC (12”x20”). I have many sizes of steel, but I can generally commit myself to 8” at 500 as a challenge, with the 66% as a check target.
Steel’s pretty cheap in the scheme of things, as long as members don’t abuse it with over-powered ammo or improper bullets and short ranges...
I have a rack which will hold my 24” round, a 66% IPSC, and a 10” round. I usually only set it up at 800-1200 yards. The 24” is almost always easy. Some days the 66% IPSC is a real challenge. Most days, the 10” is a confidence killer anywhere past 800.