Basis: the American Red Cross list for a family of four, expanded with bleeding-control supplies (Stop the Bleed) and pet supplies (AVMA). Store it in a water-resistant box or bag, in a cool place that's easy to reach (not in the trunk). Also put together a smaller version for the 72-hour bag and the car (chapter 2). Check expiration dates every 6 months.
Bleeding control (up front, within reach)
Wounds and bandages
Tools and protection
Over-the-counter medications (always follow the label)