Chess question about how to logically plan to become an FIDE master. I got about 3 years to prepare.?

According to "Rees Your Chess", endgame theory is *crucial* for creating a strong game. So much so that the book begins with teaching you rook and pawn endgames. Personally, I have encountered a lot of problems with my lack of knowledge of endgames, but thankfully have had enough time on the clock to muscle through it (usually). I would highly recommend looking into endgames as soon as possible.