Choosing the Right Boat

[houseboy]

Newbie on board. So I will try to post this question in a reasonable manner. I will be sailing in the S.F Bay area looking to venture out beyond the "Gates" on weekend excursions. I have lots of weekday time on my hands for the sport.

Some sailing experience will be taking BKB and advanced Keel Boat this winter. Most of the time I will probably single hand it (unless I meet other people). Will probably buy an older boat to scratch this itch.

I sense that it is pretty hard to test out different boats, so if you cant, then what would be a good sailboat to start with and not want to move up in size too soon? Or, something I will regret having if I sail another boat.
Kindest Regards