@jnl BudgetBytes was my go-to in grad school. I don't really use it now (I have gotten a lot better at cooking and I rarely use recipes), but it's really fucking useful if you are an unsure cook, unused to cooking most of what you eat, etc. Recipes are all pretty easy and they help you think about pricing it out per serving, if that matters: https://www.budgetbytes.com/
otherwise: if you can, split a Costco membership with someone else. plan trips together; split items that your household wants but you know you can't eat all of (for us, that's usually meat etc, because it is cheaper there per pound than most other places).
also, this is a weird one, but: you are probably using too much laundry detergent. bad for your washer, bad for the environment, costs you a lot of money. Details here: https://www.nytimes.com/wirecutter/reviews/stop-using-so-much-laundry-detergent/