a) get started on something - if you can't decide, roll the dice and pick something at random

b) ignore everything else until you are done

c) repeat

Don't worry that at your pace it will take ages - very soon you will develop an idea how to rank what you should look at next. If you don't, go back to a).

Obviously it's useless to think about it too much when your knowledge about a subject consists mostly of holes and gaps, so first gather data (a).

I can't quite see how concrete your question is, but try Khan Academy. Follow the suggested order if you have no preferences.