Haven’t done my RS GCSE yet, but I got full marks on both of my mocks (Hinduism and Thematic) as my school hasn’t completed Christianity just yet.
Unsure of your exam board, I do aqa. All I really did for the exams was use the textbooks my school gave us- the Oxford aqa Hinduism and Christianity books.
Using these, I would learn two pages, or a small topic, each night. I find it’s a memorisation game for most of the questions more than understanding the concepts, you may disagree. As long as you’re intelligent and can write an argumentative essay, you’ll be fine for the longer 12 mark questions.
Also: with the textbook I recommended, whilst it is really helpful in my revision, it does contain a lot of irrelevant information that won’t be much use in the exam. It’s vital that you filter through the content you actually need, so make it really condensed. For RS, it’s an easy GCSE I find. You don’t necessarily need notes..