I’m in a few but as a general rule I try to avoid most of the ml instance communities because some of them can be a bit on the toxic side.

Generally I stick with the ones that are on the same server as my account i.e. !linux@lemmy.world on my lemmy.world account and !linux@programming.dev on my programming.dev account with exceptions to ones where I don’t have presence on that instance, or I have limited purpose of having an account there (i.e. my lemmy.blahaj.zone account only serves to moderate the Aroace and Agender communities), in which case I usually choose the one which has been most reliable. Part of the reason I did it this way was because in the early days when Lemmy.world had load issues and was being DDoSed federation would have a lot of issues,