I have a small (30 gallon) tank, rarely have hook ups and often camp where it is difficult to obtain water. Since I often camp in desert areas or do a lot of hiking, a daily shower is all but a requirement.
For camping by myself, water use is about 3 gallons/day. About 1 gallon goes for a shower: wet down, soap up, rinse off. About 1 gallon or more is for drinking. The remaining gallon goes for cooking and cleaning dishes. Typically cleaning dishes would be about a cup of soapy water in a dirty frying pan or cooking pot. Use a paper towel to wipe down and clean the pan, silverware, dish(es). Rinse with a trickle of water. When water is really scarce I use disposable paper plates but still use the regular flatware.