If you have a refrigerator, you can buy frozen veggies that you can cook in a microwave - assuming that you have one. You can buy frozen veggies for a fraction of the cost of fresh and they are just as good for you. Add a meat, eggs, dairy, etc to get your protein, bread or cereal to get your whole grains a serving or 2 of fruit every day, some healthy fat, such as olive oil, and avocado in your salad.
You can actually buy a head of lettuce, tomato, cucumber and other raw veggies that will make a couple of meals, less expensively than you can buy a ready made salad that will only make one meal. Or buy a larger salad and split it into 2 meals. Again, this all assumes that you have a refrigerator to keep food fresh.
Eggs are relatively inexpensive - an omelete filled with onions, spinach, mushrooms and whatever other veggies you like would make a great breakfast or dinner.
You don't have to eat organic, you just have to shop wisely and wash all your food well.
Get the ready salads from super market along with the chicken if you can. Focus on green stuff and pure protein. Any ideas?