I have tried them. They do have a positive change as long as you keep wearing them. If you stop, your body seems to revert back, unless of course you do something in the meantime such as lose weight or fat.
I would be careful using them, read all you can about the safe use of them. The waist training can provide a nice look. They do give you what I call fake curves.
I do not wear them now. That was back when I cross dressed. I am a MTF transsexual now, and wished I had more real curves, but it has been many years since I wore a heavily boned well made corset.
Cheaper corsets are probably like most others things, you get what you pay for. But it may but just fine to use an inexpensive one first, then if you want to continue with waist training, to move up to a higher quality corset. But as with anything, you can spend lots of money on them.
Some people wear them as outer clothing. I never did. Have fun exploring and learning!
Chrissy