Honestly your GCSEs are not going to make any difference in the long term, outside of English Language and Maths (which are mandatory) to ensure you meet basic literacy and numeracy levels. Just pick the options you enjoy the most - don't take a language just because you feel you "have to" (I did this, managed to somehow scrape a B in GCSE Spanish, and some 10 years later cannot speak, read, understand or write a word of it) for example. The actual grades you get make more difference than the subejcts taken.
Universities don't care what you do at GCSE, as the essential subjects are all national curriculum subjects you have to do anyway - and as an extension I assure you no employer is going to care beyond the possible exceptions of those NC subjects. The one exception is that UCL has a "language requirement" that all students there have to have the equivalent of GCSE level in a foreign language by the time they graduate. Thus, you can complete this requirement once at the university. Beyond that, as above the only specific subjects they will pay any attention to are English/maths/science - and if you're specifically applying for language related degrees (including classics/ancient languages or linguistics, potentially), a language. However if you're likely to do such a degree, you probably enjoy studying languages already and plan to take one or more anyway.
A few 6th forms/colleges/schools may prefer students have done a given subject at GCSE to continue to A-level in that subject - this isn't uncommon for History/Geography, and of course is normally necessary for languages. It's often preferred for visual and performing arts subjects to have taken the relevant GCSE (drama/art/music) although usually if you can demonstrate talent in the area this can be worked around. Of course, you will probably be planning to take that subject at GCSE anyway if you want to continue with it. Which brings us back to the original advice of sticking to what you enjoy (and perhaps to an extent considering what you're good at).