A basic kit should have 3 days worth of supplies for each member of your family, including pets. You should not count on access to ATMs, stores, water or food and have a bag ready to grab with no notice. An emergency is by definition something unexpected and planning ahead is the only way to prepare.
Disaster kits are easy to make, but they are also easy to buy. Here are some resources, including helpful videos, that may help:
Video: Create an Emergency Preparedness Kit – FEMA
Video: What’s In My Kit – American Red Cross