Econplusdal on yt and PMT notes helps the most with revision for me. My exam board is OCR but I think all the exam boards have similar content anyway.
If you're struggling with what to revise I'd say best topics to go over are macro-objectives (start with easier ones like inflation/economic growth), factors affecting demand/supply, elasticities (especially PED), and fiscal/monetary/supply-side policies as there's so many essays that you could relate these to.
Don't stress too much about diagrams. You can start with simple ones that can be applied to lots of questions such as the PPC or demand/supply (or AD/AS for macro). Don't waste time trying to learn super niche ones since you most likely won't remember.
Is there something specific you're struggling with?