What vegetables/fruits can i add in my dogs food?

okay.. sorry but i just can't afford to feed my dogs the best dog food out there, one day soon if i get a job I will buy them the good food. but right now i feed the kirkland dog food. which i heard is okay, but i wanted to know what other things can i feed them, so i know there getting enough protein and stuff.. oh and i will not be going raw, 1. my freezer is too small.