Resident cat lady here!
Cats are seriously the best pet ever. Not letting them outside is an excellent idea. They get run over by vehicles, tortured by assholes, get into fights with raccoons/foxes/other wildlife, and can outcompete some native mammals for food. It's never a good idea to let a kitty outside!
Cats cannot eat chocolate. They also, like dogs, should not eat garlic or onions. Lots of plants are poisonous to them--if you google "plants poisonous to cats" you'll get a very helpful list. Note that most types of lillies are pretty deadly, so you wanna keep the cat away from them at all times.
FOOD:
It's important to feed a car (or any pet, really) a decent food. Something like Meow Mix is akin to a human eating McD's all day every day. If money is no object, think about feeding Wellness, it's about the best you can buy. Felidae is also pricey and hailed as a good food, but I don't care for it myself because it's all life stages and kittens, adult cats, and seniors do have different dietary needs. I feed Chicken Soup for the Cat Lover's Soul. It's $27 for an 18 pound bag where I am. That's about what you'd pay for Science Diet, but NEVER feed Science Diet haha. It's not a bad food, but it's not that great either and it's not worth the price. IAMS is an okay food if it's all you can afford, but I wouldn't go cheaper than that.
People used to think wet food was bad for a cat's teeth. This isn't true. Actually, because wild cats are desert animals, they don't drink much water and get most of the water from the food they eat. That's why lots of older cats today have kidney problems, because they were fed a diet of dry food and it just wasn't good for their kidneys over the long term. I learned this the hard way, and now I supplement with wet food for both my cats.
SHOTS:
Cats are required, at least in PA, to get rabies vaccines just like dogs are. As kittens they get a series of vaccines which will include distemper and probably feline leukemia and feline immunodeficiency virus. Some people give boosters of these shots, but some don't. I don't, partly because of the cost and partly because my older cat is already in kidney failure and I don't think she needs anything else potentially hurting her body.
SPAY/NEUTER:
Please do this! There are so many unwanted kittens and cats who get put to sleep every day because people don't bother to spay or neuter their pets. It's a simple procedure, the recovery is fast, and it's better for their health. Unneutered males are more likely to mark their territory, try to roam, and get into fights. Unspayed females are also more likely to try to roam, and they cry and moan while in heat, and they can develop deadly infections of the uterus and uterine/ovarian cancers.
DECLAWING:
Please don't. Declawing isn't just cutting nails, it's cutting the first knuckle off the 'finger' joint so that it doesn't grow back. Cats walk on their toes, and this fucks up their balance. They can have joint and back problems for life from being declawed. My oldest girl is actually declawed, my parents did it when I was 10. She recovered okay, but her paws kept bleeding when she came home and she didn't walk well for a while. She also doesn't bury her poop in her litter box, which happens a lot with declawed kitties. Also, what happens sometimes is that since a cat can't scratch anymore to defend itself, it will become a biter, and you don't want that at all. A cat bite is way worse than a cat scratch!
ADOPTION:
A great idea. A shelter cat will likely already have all its needed shots and will be spayed or neutered. You'll also be giving it a second chance at life.

My local SPCA charges $55 for a cat adoption, and it comes with all its shots, spayed or neutered, and microchipped. Getting all that done at a vet would be at least $250. Excellent deal lol.
To end the longest post EVER, get a cat and be cool about it. Cats are fucking great.