Khan Academy is pretty good, though in my experience most of the videos focus on the way high-school courses are structured rather than teaching in a method tha

Khan Academy is pretty good, though in my experience most of the videos focus on the way high-school courses are structured rather than teaching in a method that is the most intuitive (if you're planning to dedicate more time than an average high-school class timetable then it would make sense to learn in a more methodical way than the "scatter shot" that most high school curricula use). Unfortunately a lot of the good "starting out" maths textbooks I know of are basically university level (though it should be noted that first-year of university mathematics is basically re-learning all of your previous mathematics knowledge but with new insights). While I wouldn't stop you from trying to read a university-level textbook, most of them are structured in a way that requires some familiarity with the topic before reading.