How sweet of you to take her in!
I'd take her to the vet and have her checked out (ear mites are common in outside strays) and get some kitten chow for her.
I always gave our kittens the baby kitten food for the 1st year like they say to. I did mix several kitten foods together so they would get used to a variety because our stores have been know to suddenly drop one brand and then there you sit without out any.
We use scoopable litter and it's not too bad. Use a short box for at first and then I'd suggest getting a taller one so the "kicking and shaking" feet don't track it around as bad.
Fuzzy blanket and little jingle kitten balls are fun -- same as with human babies, nothing that can be torn off or eaten please.
Ribbons, strings and toys with cords need to be put up when they aren't being played with as they will get wrapped up in them.
Scratching post right away. We trained ours to a "fly swatter" so there was never any use of human hands to be afraid of. All you had to do was snap it on the ground and then show it to them...worked for the gobs of kittens we had.
Lots of loving and petting and cuddles. If you want it to like water, start bathing it now ... we used Johnson's no tear baby shampoo...keep water out of their ears! Our cats have all liked water and don't fuss about it. In fact they run to the tub when you run it.
Good luck and happy times ahead!