The kind of exclusive cliques you are looking for pretty much only occur in a few scenarios:
It's also worth noting that most people will not bother to maintain the kind of extra exclusive cliques you saw in school unless they have the time to invest in the heavy amount of socializing required to maintain these groups. Kids have a lot more free time to do this in high school and university; once they graduate, many of the cliquey exclusive girls and guys are too busy with their jobs to worry about maintaining the same level of cliquey exclusivity.
Instead what you get after school are different people doing exclusive cliques: socialites/children of the wealthy who don't have to work much/at all, and can spend money going to high end/exclusive clubs and parties to see and be seen; nightlife industry workers, whose jobs double as cliques and allow them to construct an air of exclusivity the mroe casual nightlife goers (all those people with 9-to-5s, who only make it to the clubs once or twice a week) must grovel to hope to be a part of; guys who struck it rich with a lucky business or investment win and now get to enjoy leisure and vacation, along with girls who decide to pursue those guys and gold dig as their sole way to sustain themselves.
You'll get cliques in some workplaces too, although not every workplace will have enough people in the same age range to make this viable.
But basically, if you're looking for the high school/university experience of joining an exclusive clique post-graduation, you will be looking at joining one of these three cliques:
These are where the air of exclusivity gets constructed in the world of grown-ups (rather than jocks/cheerleaders and frats/sororities, like it is in school).
There are also the "exclusive for that small town / that workplace / that hobby" cliques.
Like, the clique in your salsa dance class, where the best dancers and a few random hot girls all hang out together and exclude everyone else. Or the clique in your office where the five cool young people are always going to lunch or happy hours with each other but rarely/never invite their workmates. Etc.