Applied math major here. I strongly recommend you don't use websites to teach yourself math, with the possible exception of Khan Academy or OCW. Most websites or YouTube are only good if you already somewhat know the math topic, and you just want a different way of explaining it to help reinforce the topic. Most websites feel like tutoring: only good for helping as a secondary source. Wikipedia is completely useless for me unless I already know the topic, in which case it is a decent reference. I've tried to teach myself math using online resources, and failed. (Note that I have taught myself C, C++, C#, Java, and Python using online resources, and I know how to use Google, but math is a lot more formal.)
I recommend you get a proper book, which is going to be more complete, will start at the basics, and then build on itself. Anyways, I recommend you learn algebra, geometry, trigonometry, and calculus, in that order. You'll also want to learn linear algebra, but you should be able to understand it after basic algebra. I can't recommend a book for algebra or trig, since I took them so long ago. Calculus by Stewart is a popular text book, is accessible, covers the complete basics, and has old editions cheaply available. (I bought mine for $5. Older editions of textbooks are dirt cheap, and have almost the same content as newer editions.) Plenty of people don't like it, and there might be better calculus text books, so I'm not saying it's the best. Strang has written several books on linear algebra, they are well written, but not necessarily thorough. Once you have a textbook on the topic you're interested in, use it to accompany Khan Academy. Math builds on itself, so you'll constantly be referring to previous stuff that you learned, and this is significantly easier with a text book. Mark it up, highlight every definition and theorem in it, and never through it away. Check out your local library, and see what books work for you, then buy them. If you have a college/university near by, their library will have the books that their math department uses. Note that they might not be on the shelves, you'll have to ask the front desk for it, and you can only borrow it for several hours.
Once you have a decent understanding of calculus, read a proper book on math thought/proof writing. The class I took on this changed my life. All upper level math books are extremely structured, and this will teach you how it is done, as well as how to structure a proof, and set notation. I read Mathematical Proofs by Chartrand, but there are others. Once you have done this, you can easily teach yourself any math topic and have the ability to understand any math paper. You can now learn real analysis and/or abstract algebra (I recommend Pinter for abstract algebra).
TLDR; Learn math from proper text books, use online resources to help you get through them. Learn algebra, geometry, trig, calculus in that order.
I recommend you get a proper book, which is going to be more complete, will start at the basics, and then build on itself. Anyways, I recommend you learn algebra, geometry, trigonometry, and calculus, in that order. You'll also want to learn linear algebra, but you should be able to understand it after basic algebra. I can't recommend a book for algebra or trig, since I took them so long ago. Calculus by Stewart is a popular text book, is accessible, covers the complete basics, and has old editions cheaply available. (I bought mine for $5. Older editions of textbooks are dirt cheap, and have almost the same content as newer editions.) Plenty of people don't like it, and there might be better calculus text books, so I'm not saying it's the best. Strang has written several books on linear algebra, they are well written, but not necessarily thorough. Once you have a textbook on the topic you're interested in, use it to accompany Khan Academy. Math builds on itself, so you'll constantly be referring to previous stuff that you learned, and this is significantly easier with a text book. Mark it up, highlight every definition and theorem in it, and never through it away. Check out your local library, and see what books work for you, then buy them. If you have a college/university near by, their library will have the books that their math department uses. Note that they might not be on the shelves, you'll have to ask the front desk for it, and you can only borrow it for several hours.
Once you have a decent understanding of calculus, read a proper book on math thought/proof writing. The class I took on this changed my life. All upper level math books are extremely structured, and this will teach you how it is done, as well as how to structure a proof, and set notation. I read Mathematical Proofs by Chartrand, but there are others. Once you have done this, you can easily teach yourself any math topic and have the ability to understand any math paper. You can now learn real analysis and/or abstract algebra (I recommend Pinter for abstract algebra).
TLDR; Learn math from proper text books, use online resources to help you get through them. Learn algebra, geometry, trig, calculus in that order.