All your basic staples: salt, flour, oil, sugar, pasta, pasta, milk, eggs
It depends. Cheap salt is just fine. And flour, unless you’re into baking. But some things can make a difference and you don’t necessarily have to pay a lot more for it.
Pasta, for example. Bronze cut pasta absorbs sauce a lot better than “normal” pasta. It looks dull, rough, and pale as opposed to shiny and smooth. It usually only costs a buck or two more. I find it’s a big step up taste and texture-wise.
Or butter. The ones without natural flavor taste better. Sometimes it’s the store brand that doesn’t have added flavor.
And eggs. Orange yolks are way better than the pale yellow ones. But those you do have to shell out for.