It really doesn't matter even what grades you get at GCSE as long as they're quite a way above average for your school even the top unis do not care. But if you for example want to take science at UNI, triple science is a must if it's available.
Oh and make sure to take a humanity and a language, traditionally, history or georgraphy and french, german, or spanish.
Don't stress GCSE's don't matter! In fact you can even take subjcets at A-level even if you haven't taken the GCSE!