Are you interested in medicine? If not, then don't go down that route just because your parents want you to do it. I'm going to assume that you're primarily interested in Investment Banking and Computer Science. (That's also because I try to avoid giving advice to medicine candidates as many of the normal rules don't apply there.)
How's your Maths? That would be useful for both Investment Banking and Computer Science (and is often mandated for Computer Science degrees). For Investment Banking you may well opt for an Economic degree, in which case Maths A level will often be mandated there too. Maths is also very flexible and can be useful in a whole variety of degrees and careers. You'll sometimes see universities express a preference for Further Maths for Computer Science too.
Beyond that, what subjects are you good at? What subjects do you enjoy? There's no point picking A levels which you think are going to be preferred by universities if you don't get the grade they want.