I would pick out the cat, and then decide what you need.
Don't switch the cat's food right away. I would leave it be for the first week or two and then gradually switch him over to a better food. This will lower the stress of the transition for him, as well as give you some time to look into higher quality foods for him. I would keep him on the same sort of litter as well, for the same reason. He'll be in a new place with the new litter box...don't want to give him any excuses not to use it (ie. doesn't like the kind of litter). I don't know if it matters so much as the brand, but the general type (clay, corn, crystals, pellets).
As for litter boxes, I have a covered one (with the flap removed), and while I'm sure they might enjoy it better with the lid removed, it would tip over too easily and they would track litter everywhere (the lid forces them to exit onto the litter mat). If you can, you may want to start him with the same type of litter box he has at the shelter and then switch him over once he settles in. I would recommend getting a large litter mat at some point as well.
I know a lot of people here are recommending a cat tree. I would too, but again, I would wait, at least until you meet the cat. Maybe he's not a cat tree type of cat. Get some basic toys (fur mice, small balls - mine like ping pong balls, and a wand toy) and get some cardboard boxes (cut some holes in them for him to crawl through) and see how much he plays with those things. A decent cat tree is a big investment and there are a lot of choices out there. If you get a cat with claws (some come to the shelter de-clawed), I would recommend getting some things he can scratch right away - a sisel post and perhaps a cardboard scratcher that lies on the floor.
Over time, you will get to know the cat and figure out what he needs in terms of toys and litterboxes. As for food, there are a ton of threads on the site discussing what people feed and what to look for in a quality food. There is really no objective "best" - it's all a matter of opinion. I would venture a guess and say that MOST here feed a combination of wet and dry food (wet is better for them, dry is cheaper and more convenient for us, not to mention that some cats won't eat wet) and MOST feed non-grocery premium to super premium foods, that have meat as the main ingredient. Many feed grain free, but some cats do not tolerate the richness of grain-frees well. Many avoid any type of by-products and certain grains/glutens. Some are ok with those things. http://www.thecatsite.com/forums/sho...d.php?t=137404
: this thread will get you started with knowing about some of the foods people here feed and why they choose them. As you will see, there is no straight forward answer to "what is the best food." If you have questions about litter, search the care and grooming forum on this site and there are a ton of threads about people's experiences with the whole gammut of choices!
As I said, I have a covered litter box...it is filled with World's Best Cat Litter, which is made of corn. My kittens were smelly and the litter box is in the small bathroom in our small apartment...I found that clay just started to smell up the place after a few days. Corn is much less smelly, IMO.
I free-feed my girls high-quality, grain-free dry (Orijen) and they get one meal a day of so-so quality wet (usually Authority). I would like them to eat more wet, but they are picky.
I had a water fountain (Petmate Fresh Flow), but they prefer to drink out of a drinking glass I have on the bathroom floor.
They have a cat bed...that one used to sleep on once in a while. One has claimed a wicker basket that I put some blankets in for her. Right now, one is sleeping on top of my printer and the other on top of the towels on the bathroom shelf. They find places to sleep...and it usually isn't where you choose for them!
We have a couple scratching posts/toys, as well as a 4 foot tall cat tree. If you get a cat tree, I would recommend just going all out and getting one that is at least 6 feet tall. Ours isn't cutting it anymore!
All this, but I have to say - if you are getting a cat out of a cage at a shelter, feeding him the food he is on at the shelter, giving him a clean place to "do his business", getting him checked out by a vet, and giving him your love, that will be all he NEEDS for the rest of his life. As you learn more and get to know him better, there will probably be some changes you will want to make. But, there is nothing else you need to do - you are already saving his life!
One last thing...if anyone (ie. the vet) suggests switching him onto a food like Science Diet, please don't do it (unless it is for a specific, health related issue that requires special nutritional consideration). It is marketed as the best and vet-recommended, but it is over-priced and no better than some of the grocery brands out there (which are not very good!).
I hope you find a new little one to bring home and have a sucessful adoption. Good luck, and continue to visit the site so you can learn more!