How many GCSEs can one take and What GCSEs are there?Watch
You have to English, maths, and some sort of science wherever you go, I think. Some have other requirements, e.g. obligatory RS/RE, ICT, or languages. Then you can choose some number of options, e.g. history, geography, music, art, etc.
privately you can take as much as you want, if your in school then you can only take what your school offers. There are subjects like- english literature, english language, maths, double science- which is core science and additional science or biology chemistry and physics, sociology, travel and tourism, religious studies, business studies, history, further maths, geography, computing, pe, classics art and media. Hope this helped!
Anyway, I did 11, and don't see the point of doing of too many more than that. You can take GCSEs out of school but you'd need to learn the content and pay an exam centre to take the exam.
There's gazillions of GCSEs but you'll have to do English lit/lang, Maths and at least double award science.