depends how you want to work, personally I took a very small bag with a pen and some loose paper and then transferred my notes to the relevant folder when I got home, I was never on campus all day so didn't need to take lunch, just my phone, keys, water and maybe a snack so I didn't need much
perhaps take what you have and if you feel you'd rather something different get it once you're there and know your schedule, although I don't think you're going to have any issue with any sort of bag really