Questions about mathematics education and self-studying are not off-topic for the site, but arguably they are not the focus of the site either.
Irrespective to this, the question as described strikes me as too broad and too vague.
It might not be easy to ask a good question about that, since you need to navigate between it being a personal question and too vague.
However, if you are in a somewhat typical situation and narrow it down to that this might work.
What you also should state clearly is if you are more after general strategies or advice for specific subjects.
For the former the site recommended in a comment, Mathematics Educators might be better suited; it is more focused on questions from the teachers perspective, but self-study questions are fine and you could try to make it a hybrid questions asking what can be done to identify gaps including the teacher's perspective, too.
Maybe for the latter too, but there it is less clear cut.