It really is a matter of signing up with companies and seeing what they offer. If you have been shopping a few months and are enjoying it, then it is time to go to the big list of companies in the first post of the first thread of the Mystery Shopping Company Discussion section of the forum and sign up with virtually every company there. Some will have shops in your area now, some won't but may in the future (and will likely email you when something becomes available) and some may never have work in your area. Typically a shop requiring more than a few sentences of narrative--such as a bank shop--will pay more than $9.
As for ratings, SASSIE generally shows you your scores on your shop log in addition to your average score and most recent score. Not all companies that use SASSIE choose to publish scores. Scores are generally not shared between companies. Generally each company scores your work done for them, whether they share it with you or not. If your shop is accepted without comment, you are safe to assume you are fine.