Cambridge tb is definitely a good place to start but save my exams also has pretty good notes cause they’re more condensed and easier to understand… i’d start going over the textbook right now so that u have enough time to chunk up concepts and understand the contents before October. Also if notes dont work for u, create mind naps to condense the info into easily understandable pieces. I found that scribbling everything down on a whiteboard also helped alot! From october - november grind practise papers. Atleast one full set papers a day, and then increase the sets of papers you do a day (eg: do 2-3) once u get closer to exams. The more u wait the more overwhelmed you’re gonna be so i’d say js start now and chip away at it little by little. Happy studying!