Get the ready salads from super market along with the chicken if you can. Focus on green stuff and pure protein. Any ideas?
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.