For two cats (from experience and rescue organization experience) I would say buy a large litter box (they call them extra giant on some), I perfer covered with out the flapping door because it is less mess.
Yes, at least a small bowl for each of them, because cats tend to eat at the same time, not always though. Cats (males especially) should not eat a lot of fish because it contains a lot of ash. Poultry is great. Water Bowl: One bigger water bowl or two small ones are good. I have a fountain waterer because I don't have to fill it up as often. I bought the small, but wish I got the medium sized one. I was surprised on how much water cats drink.
Beds: There is a bed called Bed Buddies Fleece Donut Pet Bed at Petco, cats love those, sometimes more than the coushy ones. Placement is trial and error. You never know what spot is best for the cats, but if you keep moving it around you will find what they like. I move the beds on occasion because my cats think it is new just because its in another spot and they lay in it a lot that day. I have a 2 yr old and a 9 mo old so I have a comfy bed, a donut bed, an enclosed tent shaped bed and one of the enclosed square style ones. It is just preference and likes. You never know what you cat will like, but the rescue may know what the individual cat has been sleeping in, especially if it was fostered. If you bring you adoption agreement from an animal rescue, most Petco's offer a coupon book with some great savings in there!!!
Litter boxes need to be away from food and water especially because of feces and cats scratch at the litter and particles fly everywhere and into the food and water. A bed could be there, but its better not to. Many people put litter boxes in a bathroom, laundry room, or closet. They do sell covers so you can have them among your furniture and no one is the wiser, but they are pricey. I personally don't like it in the bedroom because cats tend to poo at night and the smell can wake you up! If you don't want to take frequent trips to the garbage (two cats go a lot!) there is a litter locker (almost like a diaper genie for baby diapers-which is great!) or if you can afford to purchase an automatic litter box those are great ($100+)! I don't have one, but I want one!
Litter: clay litter isn't the healthiest for both cats and humans to breathe in. Try to look for corn, wheat, or some other product not containing clay. We use Swheat and I love it.
Note: if you adopt kittens, many kittens don't like catnip until they start to reach a year or older, so they may or may not play with catnip toys, but toys with strings on them are great as well as, mice and balls.
Note: Males tend to be more outgoing/social than females, so two males are great or one of each, so you have a little of both worlds (I have one of each). It's up to your own preference of course. Siblings are the easiest if you are lucky to find a pair you fall in love with.
A lot of info, but I thought that it would be helpful since you will be a first time adopter. Have fun!!!