Hello there Oddball. I've been a vegetarian for 12 years, hopefully I can be of some assistance.
First of all, do you eat dairy/eggs? If you do, they can be good sources of some nutrients. Whether or not you do, though, there are plenty of choices, and I'm sure, some lower-cost ones.
1. Beans are your friends. Many nutrients, tasty, usually pretty cheap. Mexican food is particularly tasty and usually cheap, though it might get a little monotonous, depending on your tastes.
2. Indian food is full of delicious vegetarian stuff. I don't have the precise recipes, but here are a few dish names to google: Bhindi Masala, Dal (sometimes spelled Daal), Saag Paneer/Palak Paneer (though this has cheese), Aloo Gobi. Some of these might be a bit complicated, but there are often microwaveable packages available at grocery stores if you don't want to make them yourself.
3. Italian food can sometimes work, especially if you eat cheese.
4. For quick and easy, it doesn't get much better than a hummus sandwich. Also throw in some greens (arugula, lettuce, spinach, whatever) and a few tomatoes or olives if you want a more varied flavor.
5. If all else fails, there are many fake-meat soy foods. They might be a bit expensive, though, and I've heard tell they don't taste like real meat. In all honesty, by now I've forgotten what meat tastes like, so I can't be the judge of that.
Hopefully that helps somehow. Good luck!