Enough for you and your dog. Enough for 72 hrs. Compact, high carbohydrate, suggested items listed separately. Soap, toothbrush, toothpaste, comb, contact lens supplies, spare eyeglasses. Compact binoculars- a useful option.
Waterproof paper is a nice feature.
Should have multi-channel capacity, and be preprogrammed with common SAR frequencies or have hand programmable option. You don't necessarily need all these signalling devices, but some way to signal long distance is useful. Enough for 72 hrs. Some dogs eat more, some eat less, so know your dog. Dish or squirt bottle to water your dog in the field.