You dont need any GCSE to become a pilot you need an never ending pocket of money
But to answer your question, I chose subjects that I thought that could help me as a pilot and also just for life in general.
Here is a list of subjects I took
maths
english
science
double science
geography
design technology
music
RE
IT
I found geography really good, it teaches you to read maps, terrain, and most important WEATHER!!!
It also includes how nature reserves are sustained and it opens your eyes a bit more to different cultures.
By the way global warming is true but its going to happen with or without humans!!!
another fun fact you learn in geography