The official camps sites do not offer most basic supplies so you have to be fully self-serviced. There is also no ATM available so bring enough cash for the fees. Bring plenty of water and of course enough food for the number of nights you are planning to stay. Firewood is sometimes sold at the campsites for 30 N$ each.
There is no fuel station inside the park. The closest stations are in Tsumkwe in the south and Divindu or Rundu in the north. Remember fuel consumption is high because you will be traveling in 4wd most of the time inside the park and on the rough sandy tracks leading to the park. So a long range fuel tank while visiting Khaudum National Park is highly recommended.