hi, the most important thing in the puppy pack is the care sheet containing the full medical records of the pups and + "instructions and advice" where the new holder can find direct and simple "instruction" on how to handle the re-establishment of the puppy in the new home with the new family, strict instruction on the well being of the puppy, general rules on how human should behave with the new addition to the family (and how to integrate the pup in the family's lifestyle), how to feed the pup etc etc important in this sheet is the contact details of the breeder that has to be available 24/7 for help, advice and able to reach the pup immediately if anything happens and insurance details done at the owner premises over the phone;
the second most important item should be a blanket or a soft bed that has been used at least in a couple of occasions by the littermates and the mother in order to smooth over the issues of separation and, thirdly, some food in order to avoid stomach upsets if the food chosen by the new holder is different from the one the pup's been raised with.
any other item i think it's superfluous, but nonetheless nice to be given when taking a new pup into the family (it goes untold that the new holders should already be well prepared before re-homing the pup)...