Jumping grades from low to high in a year

Do you mind giving a full list of your subjects and what grade you're on each one?

Now, I never revised for GCSEs, did minimal revision for A levels, did very little revision for 1st and 2nd year of uni, and then studied ~10 hours a day 7 days a week for final year of uni (I just finished exams a few days ago!). So, any advice I give will probably be a general advice regarding grades. Don't feel like it doesn't apply to you though because you're on GCSEs - it'll apply to you for the foreseeable future.

My GCSE grades were fine even without revision (mostly A, no C), but A levels were detrimental without revision. There's no magic wand to just suddenly improve your grades, but it'll be a gradual process. To put it simply, you've got to study. Literally no other way. Don't bother cheating. Just study / revise.

How you study / revise may very well depend on the individual and subject area (hence why I asked for a full list!). Mindmaps, as you mentioned, are a waste of time unless you just want to seem busy. What I've been doing over the past year was to read any material before covering it in class to have some sort of idea, make full notes, and go over it after class.
By 'go over it' I mean spend 6 hours on a certain part of your note that was even remotely confusing every day after class. After that, rewrite your notes, so this time you fully understand every aspect of your notes and it'll help memory-wise to repeatedly write the same notes over and over. By doing this every day for the past year, even alongside job hunts, I've averaged 80% this year (1st), which improved upon my 64% in my 2nd year (2:1) to graduate with a 1st class degree.

Basically, read and write notes, and repeat it non stop, so you understand everything that's going on. Writing notes can just be from a textbook you're given.

You don't have to go this extreme as you're not on a final year uni level, but the point is that you need to find a way to be motivated and proactive. Stay away from your xbox / ps4. Think about what you want to do career wise, and realise that in order to achieve that, you very well may have to start improving your work ethic and motivation levels.

trust me, download anki on your computer. it's kinda ugly and confusing but its free and if you don't need to change any of the settings at first until ur familiar with it. it uses an algorithm called space repetition. this is literally tried-and-tested one of the best ways to absorb information. this website goes into it pretty well
https://ncase.me/remember/

just remember to keep things short, honestly u could get a 9 with the CGP textbooks so just stick to those for sciences. also look at mark schemes coz those are often repeated.
with english it helps to really know the themes, characters and quotes for both of them in depth. use anki to memorise quotes & also make essay plans
english language u kind of just have to practice with papers if ur not naturally good. whatever u do make sure ur comfortable with timing

ur set to get good grades. getting straight 9s is fckin hard— my friend did and she revised like all day every day and didn't go out for most of the year. ideally start revising over xmas for mocks, but only light revision coz u dont want to burn out then. by the time its after mocks ur gonna want to be properly revising at that point. but i wouldnt worry coz honestly gcses aren't that hard if u just know ur stuff. my mocks were like 4,5,5,6,6,6,6,7,8 and i ended up getting 7,8,8,8,8,8,9,9,9. personally wish i had gotten 2 more 9s coz those were subjects i thought i was doing well in but i just got cocky and ****ed up exam timing lol (english language). but yeah just goes to show u can literally pull them up as late as march tbh. just depends how much u wanna stress urself hahaha. my advice is don't and just start revising a bit earlier. good luck, remember gcses literally mean nothing unless ur trying to go to oxbridge xx