>>11399907I rate Israel Gelfand's books. You can work on a particular topic at a time. The coordinate geometry one is tiny, the algebra one is slim and the trig. one pretty comprehensive (obviously start with algebra if you go down this route).
I also recommend NJ WIlberger's history of maths series (on Youtube) in conjunction with the book the course follows, if you don't mind the expense. You can follow it without the text though.
Finally, I highly recommend supplementing any particular topic with further independent research. There are plenty of good maths blogs and articles out there, and you never know what kind of interesting maths you'll come across. This will probably help you more than anything. E.g. if you've learnt how to factorise and done a couple hundred questions from a textbook, next look it up online. Are there different kinds of procedures? Can you explain in english what you're actually doing? What is the relationship between a particular method and the coefficients/exponents of the terms? Passionate people with a lot of time on their hands go in to these kinds of things in depth, so look it up.
The problem with self-educated maths is that the resources are so vast, and everyone has a recommendation. In order to keep track of what you're doing, you should keep good notes (not so much for re-reading, but for reference). This will help orient you and let you know, at a glance, what content you've covered.
I don't like Khan Academy, but you may find it useful and it could also help you keep tempo through the material you need to learn if you watch X no. of videos a day or something.
