It depends on how much you wanna spend. I’m going to be at Watkins Glen again on July 13-14 (reg’ing now actually). I’m going w/ a BMWCCA chapter. if you want to register w/ a BMWCCA event (local chapter is Patroon), then you can go on BMWCCA’s site and then buy a membership then you’ll be eligible to register for any event the BMWCCA is putting on. then join motorsportreg.com and you can sign up for BMWCCA events.
Other clubs such as SCDA and Trackdaze are good stuff too, I just have the most experience w/ BMWCCA and their formats.