Realistically, how would I start to learn sewing techniques to make/modify my own clothes?

I know the basics of the basics, some crossstitch and that's about it, but how would I learn more complex techniques if I want to up my skills? Are there any good resources online or books or recommendations that you guys have?
Realistically, I know it's gonna take months or years untill I can get comfortable with it, and I feel like it's a skill that's hard to get into because there's just so many techniques around and everyone does them differently, that I don't know where to get started... The goal in this is to be able to make clothes for myself, not from scratch of course, but enough to get a finished look...