If your dollar store has a frozen foods section, see if they offer stuffed shells. Someone mentioned them in another thread the other day and said they were quite good.
I kinda see dollar store foods more as extras, sides, and supplements. I'm not sure how many main courses I could get outside of basic pasta. Speaking of pasta, what about pasta salad? The dollar tree often has roasted red bell peppers in water (jarred), small cans/jars of olives, garlic, and the pasta itself. Add maybe some onion and some leftover shredded chicken or some canned tuna if you need meat in it. A good stretchy dish.
Another side option outside of canned fruits & veggies, could be crackers along side some sliced cheese and some tuna or chicken salad. Add some fruit and maybe some cookies for a nice easy lunch. This is something DD & I have frequently for lunch. It's a favorite around here.
A simple pineapple cake is made mixing 1 box of yellow cake mix, 3 eggs, and 1 can of crushed pineapple (juice & all). You don't need anything else, but it's good with whipped topping on top.
Good luck in your search for menus!