yogurt, fruit, cut up veggies (celery sticks, baby carrots, radishes, cucumbers, broccoli), nature valley has gluten free snack bars, nuts, cheese
2 corn tortillas are great with cheese in the middle and either cooked in a skillet with a cooking spray or even directly on the flame and crisped a bit or you can make so many different kinds of tacos or tostadas, cereal such as rice or corn chex is awesome! even without milk you can take some in a baggie in your purse to have a handy snack
if you can't find gluten free pasta, then if you can find corn meal you can make polenta which is very versatile if you like italian food. Many possibilities with polenta. Also, baked potatoes with all kinds of toppings. You can just stick them in the oven when you are studying. The microwave makes a decent baked potato, too.
I got lots more, this is just off the top of my head. Hopefully this will help you come up with ideas with foods that you like.