I was just wondering how many sister groups other users have, how big your buildings look as a result of it, and how you manage them in general :)

My current save-file has 5 sister groups, I think i've used up about seven floors, mostly with break rooms, doctors and offices. It's pretty much impossible to have all of them release a single within one month because there is only one player character to write lyrics for songs. I usually have the two highest earning groups + the original group to release a single then alternate between the other three sister groups. If i'm not working on any concerts or shows I can sometimes get 5 singles out but I've yet to mange to get all 6 groups releasing one, though i've gotten really close, usually missing the end of the month by a few days.  I've purposefully kept two of the sister groups with a small member count because it's a nightmare trying to find specific girls to talk to, especially because I went with a theme of all my idol's having black hair. I'm at the point where money isn't really an issue for me so I don't take my management as seriously as early game. I'd recommend always doing your first sister group appealing to hardcore fans because I find them easiest to appeal to early on :), my first sister group actually tends to earn the most for me every month and the idol who almost always centers for them has won my elections for 4 years in a row.