Just finished Year 10. You don't need to do anything now. Once you start, make sure you review everything you learn. Make notes, flashcards etc. Treat each test like it's a real GCSE exam. Once you get into Year 11, the notes and flashcards become very useful when you revise. Saves you time in Year 11 as well, especially when getting out coloured pens and highlighters will be wasting your time, when you should be revising. Once you think you're content is good in certain topics, do as many practice papers as you can. But tbh, Year 10 isn't too bad, you just have to actually do work in class, rather than saying 'I'll do it later' because later never exists
I didn't take similar subjects, but for French , i recommend going over grammar you learnt in year 9. I think if I had done this for Spanish, I wouldn't be getting mixed up between tenses. So do go over that. For art, a few of my friends that take it, say its very time consuming, so you could do pieces of work that could improve time management. I'm not sure about history, since I don't take it, but I guess it will be fine if you pay attention in class and go over it constantly.