Depends on what you need, I suppose. This resource is said to be pretty good: https://www.susanrigetti.com/math

I decided start with Calculus I on MathAcademy because that was the last thing I did in High School. MathAcademy disagreed and told me to do PreCalculus and even bits of Algebra II first, but I knew better (MathAcademy was right and in hindsight I should’ve just started the Foundation courses to build up my pretty weak algebra skills again).

For Calculus I simply use the textbook that’s recommended at the link above. As far as I can tell, it’s good. I don’t do the problems, though - for that I use MathAcademy.