What size USB Flash Drive should I purchase?

I’m looking to purchase a USB Flash Drive for when I go back to taking classes on Monday. My old Flash Drive corrupted, so I need to buy a new one. I already have an external hard drive, but I’m looking for something more portable. FYI: I’m a graphic design major so I deal with a lot of big flash/ai/psd/etc files, but I don’t plan on putting a lot of files on it at one time – that’s what my extermal hard drive is for. (It’s just a pain to have to plug it in every time I switch computers in class, so I wanted something smaller, too)