I was talking about doing Economics at uni or PPE. For those, you need Maths. From memory, for Cambridge or LSE you also needed Further Maths. Even Oxford PPE recommends Maths strongly.
So if you are doing Economics just as a third subject and have no interest in doing it at uni, that is fine. Or let’s say you definitely want to do Law and you already have English and History then fine, Economics may make sense especially if the aim is corporate/finance law.
Or if you definitely want to study Geography then you may not need the Maths.
However, the best uni applicants are those who look ahead at the top institutions and their requirements and work their way back from there.
My DC are at selective schools so the kids tend to do things like Maths, Further Maths, Economics and History for PPE/Economics type subjects or Maths, Further Maths, Physics and Computer Science/Chemistry for Science/Computer Science/Maths/Engineering/Medicine type subjects. Those aiming for law tend to be doing English plus History and a Language/Economics/Maths and the schools advise them on those lines from when they choose their A level subjects.
So OP I strongly recommend he tries to at least aim for something that may interest him at uni and work back from there. He sounds like a high achiever and it would be a shame if he cannot get on a top course because of his A level choices. It is very annoying that the uni system works like this and they sort of have to figure it out in Year 11 because it really is so early. However, that is the system we seem to have. And yes, lots of people will pile on and say you don’t really need to do that - but in reality you are competing with others who have done precisely that.