hey :) it really depends on your budget, body type and what kind of shape you’re looking to achieve as to what corset would be right for you. The brands I have personal experience with are Isabella Corsetry, What Katie Did and Mystic City Corsets. Out of those the most comfortable was probably Isabella Corsetry but that might be different for you. My biggest recommendation would be to watch all the videos on Lucys Corsetry (if you havent already) thats where I started out, and they are honestly the most informative place for corset information online. She has reviews up of lots of different brands as well as heaps of extra information :D
Since you are looking for back support though, it might be worth investing in a custom made corset so that you’re specific needs can be more easily met, up to you though! I believe Lucy has a section on her website called Custom Fit Corsets for Under $200 or something like that which might help.
Good Luck! :)