Hi there! I was one of those kids that studied for English when the exams were right around the corner, and I can totally understand the feeling of wanting to prepare earlier instead. I personally recommend reading your prescribed and related texts early then start compiling quotes, resources etc. from them all. Preparing your notes early allows you to immediately start writing practice essays and paragraphs. If you plan to revise consistently and constantly, I think even writing paragraphs, creating essay plans or practicing writing an essay every weekend or a couple times a week is already super good. After, give those in to your English teacher and get feedback on them!
I think the best routine one can have for English is getting the quotes and notes stuff out of the way earlier, then spending a chunk of time in your routine doing practice, practice, practice. Practice writing, remembering your quotes, creating essay plans, getting feedback etc.