Saving time is precisely the reason that I attend all the events that I can, for as long as I can. I always join the Brainiacs when I'm attending Foxbury Institute because they give extra credit to Seasoned Members for all majors for attending their events and that makes it very easy to get perfect grades. I can usually reach Seasoned Member in less than one session by spamming the organizationial interactions. After that, I use the remaining meetings to do homework, prepare presentations, and write term papers. These are tasks that I would be doing anyway, so the meetings aren't wasting my time.
I also join the Bot Savants when I am studying Computer Science, Physics, or Villainy at Foxbury Institute to get even more extra credit. Similarly, I join the Art Society when I'm studying Art History or Fine Art at the University of Britechester and I join the Debate Guild when I'm studying Communications, History, Language, Psychology, or Economics at UBrite. I don't usually bother joining the Spirit organizations or the Secret Society, because they are not as helpful.
That only leaves Culinary Arts and Drama as subjects that I have to study without getting extra credit. My solution is to start those two majors at Foxbury, so they can benefit from the Brainiacs, and then switch to UBrite for the final term so I can get the Distingushed Degree.
As for the Sports and eSports teams, there's really no reason to join them unless you plan to join the Pro Athlete branch of the Athlete career or the eSports Gamer branch of the Tech Guru career. They do have nice scholarships, but the teams count as careers and they don't pay you anything except the scholarship. You can probably earn just as much or more, in less time, from money-making skills like Painting or Gardening, or a Freelance career where you can set your own schedule.
Feel free to use as much or as little of my advice as you choose. I don't let other people tell me how to play so I don't really expect anyone to listen when I telll other people how to play.