The main purpose of Gold and Silver is that you can "cash in" and use it to buy what you want.
We recommend buying coins with a United States seal on it, or a nearby government, such as Canada. People will have the most faith in them. Most people will be skeptical of some "commemorative" coin. Go with what will cash in quickly, so you can eat and function in times of emergency.
The Gold and Silver Buying Club provides a way to get in touch with people in your local, trusted area, who will trade gold and silver for cash.
PreservationOfWealth.net/club also buys back gold and near spot prices.