I'm not a user, but I am a new agent, so I can tell you a few things. The medicare supplement plans are very regulated. They are named A-N. Not every insurance company has every plan, but the plans are the same across insurance companies in terms of coverage (ie. a J plan is always going to cover the same things no matter which company sells it to you) You can go to medicare.gov and find a lot of information, including charts about what each plan covers and pick the one that's right for you. No one can tell you which to pick. It's going to depend on your wants, needs, and budget.
This might be a useful link to part of the medicare website:
http://www.medicare.gov/find-a-plan/questi
ons/medigap-home.aspx
Just put in your zip code and it gives you an estimate of the yearly cost, what each plan covers, and links to a list of companies that offer each plan. Once you pick what you want, you might want to contact agents for those companies in your area and talk to them or go to the company's website and get some prices if there are no local agents (or they might have a "find an agent" link on their website).
I hope this helps and that you find a plan that works for you.