If you want to go it alone. I suggest looking at the university or college you are interested in. Look up the syllabus for classes you would want to take. Find the text book the teacher uses. Buy the text book which can be upwards of 200$ and read the text book. The 200$ is worth it because if you were actually going to college u would be buying the text book and paying for the credit on top of that. The text book is all you need to learn most subjects. Most college students hardly do the reading, so if you can do the reading you will get it better than most. Depending on the kind of learner you are though, you may need hands on. So you could get the lab books and try doing the exercises but you may need to spend a lot of money on equipment depending on what it is.
If you make it through the text book, you can pay a few bucks and just take a test through the college board and get actual credit for it that could be transferred to a college in the future.