Not an English student so I can't offer specific advice, but for me studying Englishy style stuff generally falls into about four categories: Reading, Writing, Revising and Discussion. Reading is pretty self-explanatory, you just need to read things. Anything is good, but make sure you vary it a bit. You're unlikely to come across more complex language in a YA novel, similarly you won't find a lot of pretty words in a manual or textbook. Poems are a good way to quickly learn new words, and there's a plethora of them on the internet. I find most of them dreadfully boring though
Writing is pretty obvious too. You can't be expected to write a perfect essay in 50 minutes if you've never written an essay before. Not that I'm saying that you should write an essay every day - most writing works. Into poetry, prose, formal or expository works, or plays? Any of those will work if you put the time into making sure they're top notch. The point isn't to memorize a perfect piece or method, it's to develop the skill to be able to put exactly what you're thinking on the page. It also really makes you think about the use of certain words, grammar in general and, in my experience, improves the flow of your sentences a lot. You don't really need feedback to improve (as long as you revise your own work), but you'll get better way faster if you give your work to a teacher or a friend or just post it somewhere on the internet for someone to tear into.
Revising is where it starts to get a bit gray. A maths analogy is probably the best way to explain - you can't know if you're right if you don't check the answer, and you can't know where you went wrong without taking that into account, or going through line by line to see where you messed up. "Checking your answer" with writing is going through your piece (preferably after at least a week has passed) and comparing it to a rubric or a set of goals you set for yourself. It's hard, in written work particularly, to be brutally honest with yourself - but it's definitely worth it. 10/10 do recommend. Going through line by line generally comes after you check your work. It's probably what you do when your teacher hands back your work. "Teacher says my contention is unclear - okay, what makes it unclear?" is the kind of process to go through there. Not a lot to talk about in this regard. Revising one essay will make that essay better, but revising 50 will make all your future essays better. The idea is to find out where you're weakest and fix it. Reading other people's work is also good if you can't be bothered writing your own essay. They'll probably appreciate it too
Discussion is arguably the most important part though. In Literature and Classics, it's pretty much the bulk of the class time. Not sure for English though, but it should be (imo). Track down a friend or a teacher and just talk about whatever your topic is, or your text. Starting off with "how do you think [idea] is represented in [text]?" is a really good way to start. Questions in general will lead you to a deeper understanding of whatever it is you happen to be doing and they're a lot more interactive than being lectured at for an hour. My favourite part about discussions is the disagreements though. As long as you can back yourself up with some good evidence, your idea is valid. If there wasn't any disagreements, everyone's essays would be the same. Imagine being the teacher that had to mark that? Discussion will make up the bulk of anything you read, write or revise. Think of it as the interpretation of evidence, if that helps. Can't really offer any advice for improving it though, it's just something that happens as you get more familiar with your topic.
To finish off, I thought I'd leave you with some interesting websites that might offer some more insight:
Arguman - Not particularly populated but there can be some interesting discussion in there.
Phrontistery - Lots of lists of cool words and stuff
Getty Vocabularies - Exactly what it sounds like
Forvo - Pronunciation guide. Ironically the title of the website doesn't give any indication.
Folktext Archive - Mostly interesting reads, but more notably they use some different language. Fun for analysis and tbh some of them are kinda funny (bald men stories amirite)
Sacred Texts - More of the same, but religious texts.
Aeon - Generally a compliation of people sharing their thoughts on things. There's a lot of essays.