Heyyy I’m in the same boat (aspiring teacher, choosing a-levels)
Do you know what sort of teacher you wanna be? Primary, secondary? Because if you want to specialise in a subject at secondary, you should definitely put that subject down for A-Level. If not, I’d recommend just taking subjects you enjoy, can’t go wrong with that! Perhaps a core subject like Maths or English would be good, but I don’t think it matters all that much.