Beans and pulses aren't expensive especially dried.
They also have the advantage of filling you up and containing protein. You can mix them with meats in stews, make soups or put them in salads.
Some are easier to cook from dried such as lentils than others such as kidney beans. The ones that are hard to cook from dried just buy canned.
I suggest you Google how you cook different kind of pulses and beans, and also recipes for all types of beans and lentils. Once you have a few ideas then go and buy some and try them out.
You will probably need to buy some herbs and spices as well but to be honest if you cook anyway you will have them in your cupboards.
BTW eggs and nuts aren't expensive either and both are a good source of micronutrients. Though don't go mad eating nuts as they are high in fat.