It’s much easier to eat veg when broke than carnivore, IME. With the exception of ground beef, some dairy, and eggs, animal products are pretty expensive.
If at all possible cook from scratch and buy raw materials in bulk. Processed, packaged foods will eat your money. This includes corn chips! You’re paying for air with those. You can get a bag of rice that will feed you for a week for the same price. NEVER eat out. It is not worth the expense!
You need to make sure you get enough protein and essential fats: eggs, cottage cheese (Which I don’t like on it’s own but can be added to many things), and butter are all fairly cheap, and full of nutrients.
Other than that I would stick to buying grains (whole preferred because they have vitamins and protein unlike white rice, white flour, etc), dry beans (canned ones are much more expensive), dried texturized vegetable protein (much cheaper than tofu, seitan, other soy stuff), whatever fruit and veg you can afford (frozen packs are a good value), and that wonderful staple of vegetarians, peanut butter.
Use coupons whenever you can. Menu plan ahead of time. It’s also really important not to waste any food. Eat leftovers from last night’s dinner for lunch. If you are going to work, pack lunch. Keep an eye on dates so nothing goes bad before you eat it and wastes money.
Breakfast: 2 eggs, pancakes with cottage cheese added (cottage cheese pancakes are the best)
Lunch: Peanut butter sandwich, carrots, apple
Dinner: Brown rice with bean and TVP chili, broccoli on the side
Breakfast: Oatmeal, with butter and nuts
Lunch: Leftover dinner from the last night
Dinner: Zucchini egg foo young (look up recipes online, it’s delicious!) with a side of veg and brown rice
Planning and a budget is going to be the key here. Google around and you can find a ton of from-scratch, vegetarian recipes and meal plans.