Best way to learn spanish through self-study?

I have been taking spanish in school for more than 5 years now, but our curriculum is not very good, so I am looking to take matters into my own hands. Even with the previous education i would still consider myself at a basic level (I know preterite imperfect and present as well as a few other but not very well and i know some vocab and i understand some grammar). What would be the best way to continue learning spanish towards fluency? Would it be possible to start where I am sort of amidst levels (basic programs cover things I already know and i haven't tried intermediate programs)?