OK, I'll admit it. My first sailboat was a 30 ft Catalina. Took the ASA sailing classes on a 30 ft Islander before I bought her. I'd have loved to be exposed to sailing smaller boats before then, but I wasn't. We sailed her for about 8 years, darned near every weekend, and the only trouble we had was running aground once or twice.
I'm proud to say that my daughter learned to sail a dinghy that we bought shortly after the catalina. Nothing quite like seeing your little girl sail around the anchorage on her own...
That said, I have no regrets about my first sailing experience being on a 30 ft boat.
Beneteau 423 #310