Just for the record, I've been to a LOT of parties, but never been to a "must play" party. No one is ever expected to play (with their partner and/or with others), even if you've done so in the past. Rules of all the venues to which I've been, and a subcultural rule as well. And there's lots of visual fun to be had if that's your interest.
Mrs. and I got our first invite the first time we went to PE. Basically, there's folks out there "scouting" for likely attendees for the more exclusive parties. He gave us a card and a name, and we went from there.
Also, many of the parties advertise on the internet. They typically screen attendees, judging them by their email responses. The first time or two your behavior is observed, and unless you're totally obnoxious or your break the rules you're good to go. And BTW, physical appearance isn't much of an issue (you'd be surprised how many people are into all kinds of different types of beauty), though for some venues being nicely dressed and clean is.
Go to enough events, the word goes around, and more invitations come your way. There's been a fair number of "private gatherings" in the Bay Area over the past few years that only select from folks who have a rep as being respectful and drama-free.
I'm far too lazy to start and moderate one, but I'd join one in a heartbeat!