There are lots of good questions on CV asking for references for self study, or for methods of learning, or other self study resources (a search for learning -[machine-learning] turns up a few).
Many of these questions are highly relevant to someone like me, who has a basic first year uni intro-to-stats course as background, and would very much like to learn more, but is feeling a bit out of their depth. But many of these questions are quite hard to search for, or come at the topic from an angle that might not be immediately apparent, so having a tag to chuck them all under would be incredibly useful.
I would suggest [self-study], but there might be better options, like a more general [education], or just [study] (although that's a little cryptic).
(I would tag this question [tag-request], but I don't have the rep)
[homework]. In particular, if users understand that[self-study]means "sounds like a homework question, but it's not really homework" this could be useful and cut down on such commentary to the actual question. Of course, that can be abused, but so can the lack of tagging as[homework]in the first place. That said, used in this way, it should not be a tag that is used in isolation (i.e., the question should have other tags as well). $\endgroup$