Surprisingly little at first. Litter tray, a few bowls for food and water (you or family will likely have suitable ones in a cupboard), something to sleep on/in (if it agrees) and some toys. Don't throw away any cardboard boxes in the near fiture - they love those and they're multi functional.
He/she will need an appointment with your vet, for vaccinations. Vet will also give them a check-up, flea/worm treatment. The fleas seem to have come out to play the last week , so also a good house flea spray like Acclaim.
A Feliway plug-in if a multi-pet household can't hurt.
Unlike a puppy, a kitten has been taught by it's mother to be house-trained. However, 8 weeks is quite young to be away from mum-cat she/he may develop a squitty bum, so the unscented (H2O?) baby wipes are kind to delicate kitten bottoms if needed after a poo. A litter like World's Best or Clumping Gold has small, round particles, so kinder to small sensitive paws.
Drinking straws are currently my kitten's toy of choice. He can pick them up and throw them
Kitten will be undeterred in trying to steal your food off your plate/out of your mouth. I let Mantrakitten taste a Pringle an hour ago and now he is tearing about like a baby elephant & keeping us awake
Lastly, don't forget to post photographs of your kitten. It's the law.