I'm a student as well, and I've managed pretty well financially.

I buy potatoes, rice, pasta, noodles, chicken, miced meat so much. That's cheap and try to buy some veggies every now and then. Also one bag of Müsli lasts long; eat it with yoghurt.

Chicken chicken chicken is healthy, good and cheap! And don't buy ready/microwave foods. You'll spare a lot when you cook that all by yourself.

Also, I often bake rolls and bread by myself. You might wanna try that out.