I don't really buy textbooks.
I budget about $500 a month for everything beyond rent, electricity, cable, internet, water and heat (which also run me about $500 a month on average. Maybe a little more when I factor in my phone bill). So the $500 covers everything from groceries to laundry money to gifts. I have a separate travel budget (LDR = 1 flight every month or so) and I allow myself to put small unexpected amounts of money, like money from participating in a study, into a separate account for little things I really want but don't have room in my budget for.
This also doesn't include my moving expenses (moving is expensive, as is setting up a new apartment) or holiday season spending (I always go over-budget between Thanksgiving and Christmas, so next school year I'll be setting aside a separate budget for gifts/electronics/other 'random' bigger purchases. $200 - $500, not sure yet).
I found $600 to be more comfortable living, but that was when I was working. Now that I'm living partially on loans, I'm willing to watch my spending more closely.
... I've been tracking just about every penny I've spent for nearly two years now. 😳 I find it strangely enjoyable.