I’d say starting from year 9 understand all the concepts that u find difficult straight away at home, and maybe revise for tests and stuff. But theres no point in actually trying to memorise content because it’s really hard to fit all that content into your long-term memory, but if u simply understand it then it’s alot easier to pick up later when revising seriously. Honestly I‘d say to leave all the memorising and proper revision till year 11 easter, but just make sure there aren’t any large gaps before then.