I did my GCSE's last year (9 subjects - with eight 9s and one 8) and this was how I revised for them.
- I usually split my work into 3 hour long slots.
- Typically spend 1 hour / 1.5 hours for each subject depending on your confidence (within the slot)
eg 1hr (chem, bio, physics) or 1.5 hr (english lit, english lang)
- on a school day I usually spent 3 hours revising after school
- I find it easier to do some work in the morning especially between 10am - 1pm (3 hrs) since time goes by really quickly
- I take an hour break for lunch and spend another 2/3 hrs doing revision.
- during term breaks (april/may) I used the weekend routine.
The time and frequency you spend on each subject depends on your confidence in the subject. For example, I struggled with english lit/lang so near the exams I spent more time revising for those. If you're currently not sure which ones to priorities I would do it in this order
1. Subject most likely to take for a level / uni
3. English Language
4. Chemistry and Physics
On average, I would aim to have each subject present in the timetable twice (within the timeslots) and every 3 days if possible (ensure they're evenly spread).
Don't feel pressured to stick to this plan, this was just what I did, and you can probably achieve better with less time. The revision technique is more important than just checking off hours. I found it better to start revising in September and build up the intensity casually while others may do better cramming before the actual exam, I found it less stressful that way. In general, focus on the subjects you're less confident on and evenly space out your revision for each subject across the week.