I'm in the same boat. I don't have a very big budget. I agree with the others- I think that rice, eggs, and beans are all very inexpensive, yet healthy. Brown rice is healthier than white rice.
Ramen noodles, can be a great way to fill up fast, although the nutritional content is not there, other than carbs/sodium - which you do need in your diet. Also, others may not think the same way but I'm a 100% in multi-vitamins. A good quality - ideally organic/natural based supplement can help you quickly, and relatively inexpensively get all your vitamins/minerals/phytonutrients without breaking your piggybank.
Just be sure you're still getting your carbs/protein/sugars. Also, drinking a lot of water helps!