Read all the Mandarin Companion books, it's fair to say comprehensible input was an absolute game-changer for my progress. The other people in my class don't understand what happened, but I'm not keeping it secret, it really did work that well. Some of the grammar patterns are even beginning to yield, in the sense that I am becoming able to use them myself.
Weirdly, from doing so many flashcards, I've found myself able to read materials phonetically (including tones) without being able to fully parse the meaning unless I re-read it more slowly. I would never have expected to experience that with Chinese.
Looking for more materials now, and will jump into the HSK4 syllabus with the intention of taking this as my first actual exam. I know it's not important but would be nice to formalise my studies a little bit.