I had to take 6 GCSE's only because of some issues i had, and so i am taking 6 only. I college i want to do A levels at gave me an exception, they only take 7 gcse's but i really want to go to Cambridge or oxford in the future and so i was thinking of studying religious studies and psychology during the summer and sitting the exam in November? is it worth it??
I guess the more GCSEs the better for uni, but remember you're gonna have quite a big workload already, so the real question is, can you handle any extra GCSEs?
It's better to have 6 good GCSEs than 9 bad ones, but if you can handle it, then sure! I mean, it can't hurt
(Don't rely solely on my advice, I'm only in year 10 XD )