If you don't already have a scanner, it would definitely be worth getting one (a cheapo copy-print-scan machine will set you back about £30) - again, this helps with the quality of the images you submit. Having a few old cardboard boxes around that you can cut up is also surprisingly helpful! Also really useful are black fineliners, Sharpies in all colours (but especially black), and tracing paper. Mostly, though, just see how you go - there's no point buying loads of stuff and finding you never use it; easier to wait and see what you're actually using.
I have a degree already, so this one is really just for fun - and actually my focus is more the Creative Writing side of my studies. Design complements it well, though - they involve similar skills and approaches.