Most Helpful Guy
Adam and Eve some places like that sexual stuff
Most Helpful Girl
It really depends on your budget, body shape, and what you plan to use it for. If you want to do waist training, you'll need a better quality corset and custom is best (but not necessary if your body is pretty average). If you just want it for fashion, a more affordable off the rack corset should be fine, but you'll still want to make sure it's a real corset with steel boning and not just a lace-up tube top. I'd recommend Orchard Corset for affordable real corsets. My favorite are the mesh ones, but they have satin and cotton too and several different styles. They'll also help you with fit if you contact them.
My #1 recommendation though would be to check out this girl's site.
She's got basically everything you could ever want to know about corsets. Hope that helps!