I attempt to write this as my cat stands on the desk in front of the monitor. Cats also love keyboards and blocking the television when possible.
First off, as others have said, no need to buy a specific cat bed, lots of toys, expensive feeders or automated litter boxes. These things will either break or go unused. Cats will pick out certain spots they like to lay in and frequent them often. You will have little to no choice in this matter - in fact, if you attempt to remove your cat from a specific spot, they will just go right back, or if that isn't possible they will find an even more irritating place to call their own.
A gate will be meaningless to a cat; they are (most of them) great jumpers, very nimble, and able to get through doors and into spots that you would have never thought possible. You will find yourself saying, "how the hell did you get in there?!" on more than one occasion.
The main thing to keep in mind is that cats very much have different and unique personalities, so you may want to hold off on investing in certain things until you know what they like. For example, I've had cats in the past that would only scratch carpet posts, and cats that would only scratch cardboard items. I've had cats that loved people food, especially drinking my leftover cereal milk, and it was a constant fight to get them to leave me alone while eating. And then I have my current cats, who couldn't care less about people food. I have two cats now, and one of them always darts to the front door and cries to get out when we open it, and the other doesn't care to go outside at all. I've had cats that will use any litter, and cats that were very picky and only used a certain brand. One of my cats loves sleeping in little cubbies and dark holes, and the other always needs to be out near the humans or he gets lonely and starts howling for us. Some like the fake mice, some prefer dangling things. Some cats love to be out among the people, others will hide under the bed all day long. Each cat will present its own challenges as well, such as my cat that eats plastic until it makes him sick, so we have to hide every plastic bag before he gets to it. Or my other cat who is jumpy and squirmy and can't sit still, so it's difficult to cuddle with her. And that's really special and different as well - the way you bond with each cat will be different.
So really, it is hard for anyone to give you great advice, until you've brought the kitty home and gotten a sense for who they are. Luckily cats are a lot easier to potty train than puppies are. With both of my cats, the minute we set them down in their new litter box they just "knew" what to do and have ever since. One of my cats has gone to the bathroom outside of the box a couple of times, but only when he's really pissed at us...that sounds funny, but it's true. Cats can be real bitches when they don't get their way.
But honestly, having a cat is so rewarding that you will forget about that kind of stuff.
Let's see...you will also want to buy a cat carrier. Doesn't have to be an expensive one, the simple plastic ones will usually do fine. Also buy a special mat or carpet (sold in litter aisles) to go near the litter box so that it catches the stuff the cat drags out with its feet. Buy a brush to cut down on shedding (and cats usually find brush time a treat). They love sleeping in boxes and bags. Some mix of dry and wet food is probably best.
Also, keep in mind that both you and the cat will need time to get into a routine. If things don't seem to be going according to schedule at first (i.e. the cat wakes you up every morning at 4 am), don't freak out, it will get better over time as you learn each other schedules and form your new rituals.
Have fun with your new kitty. I hope that everything goes well for the both of you!