Should I take AS exams?

Im in Year 12, I really want to go to Oxbridge and My GCSEs are 9887777777664 and apparently thats a predicted ABC in A-level. RN i predicted higher than that but personally i'm aiming for 5A*s in Mathematics, Further mathematics, Economics, Politics and EPQ. I've been told that if i take AS exams it'll prove my predicted grades more but it is also expensive (not sure if my school will fund it) and i'm not sure if it would be worth the hassle.
Should i take AS (it is already compulsory for Further maths at my school)? and what should i do to increase my chances of getting in to Oxbridge and other top Russell groups? (Im already doing lots of super curriculars) - Course subjects i'm considering (PPE, Philosophy, Mathematics, Econ, CP, Politics etc. i hope to make a decision by April latest)
Thank you! - also do you know anyone who got into top unis with similar GCSE grades without extenuating circumstances

Your gcse grades do not count you out from Cambridge, probably too low for Oxford, but your a-level predictions would have to be at least all A if you intend to apply to either.
All you can really do now is to make sure you get minimum A's in your a-levels so when you apply in year 13, you will have A's predicted.
You must remember most applicants to Oxbridge have an average of around 8.5 across their gcse's and they will easily get A-A* in their a-levels, so you would have to keep up to have a chance.
Good luck!

tbh i will give cambridge another try but im really interested in Oxford especially after talking to students and seeing it for myself. Should i take AS to prove my capabilities and do you think slightly exaggerating circumstances at both GCSE and A-level can help me e.g. dog passing away

Remember you can only apply to one
If you need to prove your worth and fast, I don't see why not, but don't go spending heaps of money on them.
To your school yes, to the uni- no.

tbh i will give cambridge another try but im really interested in Oxford especially after talking to students and seeing it for myself. Should i take AS to prove my capabilities and do you think slightly exaggerating circumstances at both GCSE and A-level can help me e.g. dog passing away