I wouldn't buy too much just yet as you don't know what the cat will be like. I bought a big basket of toys and they have been mostly ignored!
The only ones mine likes are the Yoweee catnip range (you can get them Amazon). The catnip is really strong - I can smell it myself. Mine has the banana and the rainbow and she carries them around the house at night, for reasons known only to her - indeed I sometimes wake up and find them in the bed next to me.
I also have a cat tree that she really likes - I would buy the biggest you have room for and can afford. They tend to come with built in scratching posts and hidey holes.
Mine also likes cat beds- I have a couple for her that we're given to me by family members - I didn't buy any beds initially as no other cat I have owned has ever gone near an actual cat bed!
In terms of litter trays I would buy the biggest you can afford, and one with a roof, as these are much better at keeping the litter in.
I would only buy smallish amounts of food, as many cats are picky eaters and you don't know what he/she will like. Mine only eats the more expensive Aldi brand of dried food - she won't touch any of the "better" brand. In terms of wet food, she'll eat anything with gravy, but not keen on pate style foods and is disgusted by anything in jelly...
And so on.
Sane with cat litter brands - they seem to have their preferences and these aren't always the best/most expensive brands!
Good luck! So exciting......