How Realistic Are My UCAS Choices?

I'm a gap year student with grades A*A*A achieved in Maths, Economics and History alongside a predicted grade A in Further Maths, so together A*A*AA.
My UCAS Choices are:
• University of Oxford: Economics and Management
• Imperial College London: Econ, Finance and Data Science
• LSE: Economics
• UCL: Economics
• Warwick: Economics
I've heard some people say gap year students are disadvantaged when applying again so idrk whether I'm wasting my choices

Never mind, ignore my comment. I just realised you didn't resit, you just had a gap year. Unis are fine with gap years as long as you show what useful things you did on that gap years.

Honest opinion - too many high-risk choices.
The Unis you have chosen are all mega-competitive for Econ and meeting, or even exceeding, the entry requirements does not guarantee you an offer. Each year, hundreds of such applicants will be rejected. This means that you risk not getting any offers at all - and with no lower grade choices at all, you will have nothing to fall back on.
The advice is to pick Oxbridge and at most, only two of the other Unison your list. Look at Unis like Bristol, Manchester, Birmingham, Durham etc, they will be less insanely competitive - and you are far more likely to receive an offer.

I'm a gap year student with grades A*A*A achieved in Maths, Economics and History alongside a predicted grade A in Further Maths, so together A*A*AA.
My UCAS Choices are:
• University of Oxford: Economics and Management
• Imperial College London: Econ, Finance and Data Science
• LSE: Economics
• UCL: Economics
• Warwick: Economics
I've heard some people say gap year students are disadvantaged when applying again so idrk whether I'm wasting my choices

I'm a gap year student with grades A*A*A achieved in Maths, Economics and History alongside a predicted grade A in Further Maths, so together A*A*AA.
My UCAS Choices are:
• University of Oxford: Economics and Management
• Imperial College London: Econ, Finance and Data Science
• LSE: Economics
• UCL: Economics
• Warwick: Economics
I've heard some people say gap year students are disadvantaged when applying again so idrk whether I'm wasting my choices

I wouldn't say that gap year students are disadvantaged, but uni's might expect a little more from you as you are one year older have have completed your A-levels, rather than being mid way through them. For example, an admissions tutor at Cambridge said that for Gap year students, at interview they could get asked any question from any part of the A-level syllabus, rather than just modules covered to date. You need to fill in a form prior to interview to say what modules you have covered so far.

Note that you don't have to apply to all 5 at once. Keep 1-2 choices back in case your top 3-4 all reject you. If that happens then you can adjust your sights accordingly.

Any particular tips or resources you can recommend for Maths, FM revision for A*/A grades? Considering taking Maths in a gap year.

I'm a gap year student with grades A*A*A achieved in Maths, Economics and History alongside a predicted grade A in Further Maths, so together A*A*AA.
My UCAS Choices are:
• University of Oxford: Economics and Management
• Imperial College London: Econ, Finance and Data Science
• LSE: Economics
• UCL: Economics
• Warwick: Economics
I've heard some people say gap year students are disadvantaged when applying again so idrk whether I'm wasting my choices

A bit too risky dude...I have few experience with gap year student so you may check each school's statement about gay year yourself and explain it very well in your PS. Only one a-level grade difference is not enough for a whole year gap.
Oxford: TSA & interview required, with 5% successful rate
IC:Their Applications: places ratio is like 35:1 in 2023, and It requires both Admissions test (TMUA) & Post-application interview.
LSE: TUMA required, and the offer rate is like 12%-15% for home student and even lower on average. Extremely high requirement for your PS.
UCL: No special requirement, but it is still a very competitive program
Warwick: TUMA required
You may like Oxford very much, but you will need to prepare for two admission tests on October with only 10 days difference, while you might be busy with further math & interviews preparation. So I suggest that if you are interested in Oxbridge then you may choose Cambridge which also requires TMUA & interview, and yields a 12.5% offer rate in 2023 cycle. But it requires A*A*A, so you better get a A* in Further Math.
It seems most of your choices require TMUA score.
Usually a score above 6.5 can be regraded as satisfactory, but top school always aim higher. So take past paper and consult with your math teacher/tutor, if you cannot have a solid 6 for now, then choose wisely pls.
Besides, if I were you, I would probably choose 1-2 programmes without additional requirements as insurance school, and only pick my fav three out of oxbridge/ic/lse/ucl for this type of competitive programme.

I'm a gap year student with grades A*A*A achieved in Maths, Economics and History alongside a predicted grade A in Further Maths, so together A*A*AA.

My UCAS Choices are:
• University of Oxford: Economics and Management
• Imperial College London: Econ, Finance and Data Science
• LSE: Economics
• UCL: Economics
• Warwick: Economics

I've heard some people say gap year students are disadvantaged when applying again so idrk whether I'm wasting my choices

For further context I got 988877776 in my GCSEs