I think you really need to enjoy Art. I don't do it, but my two best friends who took it at both GCSE and A Level have had very mixed responses to it. One friend who is annoyingly good at doing work he doesn't want to do acheived what he needed for an A at GCSE in a few weeks. My other friend who is inversely lazy got his in at the last minute after working extremely hard at the end. He still got an A. They say it's extremely easy, but extremely tedious, but then, they're very good at Art from what I see, so that's something to consider.
RS is bull**** and should be ignored (it might be a more useful/interesting GCSE if your school offers it as an option rather than a mandatory subject).