Are you cooking for one or a group/family?
I batch cook, buy meat and veg etc on offer accordingly. I make lasagne, tomato chicken, pasta bake, cottage pie, hotpot....the options are endless. I then put in tupperware or disposable foils for oven or microwave.
Its quick to chop a load of salad once a week and store in separate containers. Then toss a bit of each together as a side or lunch.
Use leftovers for soup to save wastage, just add stock and lentils/beans and blitz before serving.
Easy and cheap
As long as you have some nutritional balance you can do that just make sure you can keep burning it and stay away from fast food. Or use these foods Put whole grain wraps in the oven and let them get crispy and make chips out of them and dip them in salsa. Or if you want ice cream go with arctic zero. You can have the pint and not gain a lb or have a protein shake with fruits. Or chobani yogurt.