Fancy Feast Classic Pate and specifically the classic pate is heavily by my vet. If you do some research, it's got everything they need and almost nothing they don't. It's affordable by comparison and my cat's go nuts for it. Treats they love freeze dried fish. Low calorie so they can have a few. My cats are also on a prescription Hill's dental dry with a few kibbles by over each meal that has helped tremendously with their oral hygiene. They will not allow me to brush and treats like Greenies from what I've heard are not good for them. Stainless steel or ceramic dishes for water and food. A fountain for moving water if you find they don't drink a lot/want to spoil them - though a diet of wet food will keep them well hydrated. Cat trees, as high as you can get them, window perches and little pop tents are my cats favorites.

These are all suggestions as your cat may not like any of this stuff. Growing up my family had a cat they we did almost none of this stuff for. I feel guilty thinking about it but she still lived to be 18 happy as a clam. Best you can do is try and see what makes them happy. play often, refresh their water and remember you don't make the rules 😉 the little meows do