The exact ingredients you'll need depend on which recipes tickle your fancy, but if you're looking to do this in an easy, cost-effective way, there are a few things I'd recommend stocking up on due to their versatility. Firstly, full fat greek or natural yoghurt: it's in the smoothies, it's in the snacks, it's even in the pizza (cycle 2, totally worth the wait). Next, eggs and cheese, because that opens up a whole world of quick omelettes and frittatas. I have a constant supply of chicken breast on hand, and I also keep my freezer full of bags of frozen chopped onion, spinach, and peppers, which I chuck into the aforementioned frittatas, as well as curries and pasta sauces.