Here is what I do. Head to your local university bookstore, and buy the course-pack for a music theory course. Read the syllabus, borrow the books from the libr

Here is what I do. Head to your local university bookstore, and buy the course-pack for a music theory course. Read the syllabus, borrow the books from the library and use the materials. You get a structured way to approach the subject and you do the legwork to learn it. It usually costs ~< $100 to get knowledge worth much more.