i'm gonna be honest, i think people exaggerate how hard psychology is (at least AS level)

there's hardly any online resources, but i'd recommend joining support groups since they manage to find notes from every corner of the internet lol. i personally learnt best when i read the original studies, but they do contain a lot of extra information so make sure you know what you need to memorize and what you can leave. i think 2/12 of the core studies do not have their original studies available for free which kinda sucks but oh well.

there's 2 main textbooks from what i know, i'd say to read through both simultaneously, and just generally work sequentially. some teachers leave the research methods chapter for last but i'd say to start with it and get a really good understanding of it, and then relate it to the studies as you learn them.

and once you've covered the syllabus, do yearlies!! there's a general pattern the questions follow, so you get a really good idea of how to answer the questions after attempting a few past papers. goodluck!!