Are you studying A-levels in England or NI/Wales/rest of world? In either event you wouldn't normally do AS Maths plus A-level Maths plus A-level Further Maths because that's not how those qualifications work.
If you're studying in England you needn't do the AS at all (and most schools don't) as it's essentially a redundant qualification once you complete the full A-level (and universities aren't going to consider it when you apply).
If you're studying in NI/Wales or international A-levels, these are on the old modular format and therefore the AS is an integral part of the overall A-level so it's not something you do "in addition to" the A-level Maths (and FM), it's part of A-level Maths (the first year of it specifically).
In any event given you're taking biology and chemistry it is fine for medicine - most medical schools don't consider both maths and FM and will just make you an offer based on three A-levels (in your case biology, chemistry and maths or FM).
The concept of a "top uni" for medicine is, incidentally, meaningless in the UK. All medical schools in the UK are accredited to the same standards by the GMC and, more importantly, the only provider of graduate medical training posts in the UK is the NHS which takes the GMCs stance that all medical schools are equal and to ensure there is no bias, blind recruiters from your medical school for specialty recruitment (so they don't know where you studied) and for foundation placement posts are issued by algorithm which does not account for which medical school you went to (by all accounts it's largely random now). Don't focus on meaningless concepts of applying to a "good" medical school in the UK, as essentially - they're all as good as another (i.e. any medical degree will get you exactly as far in a medical career in the UK).
If you're not applying to medicine in the UK much of the above may not apply - this site is oriented towards people applying to study in the UK.