That just depends on the states you'll traveling in. For my needs my SC and my NH non-resident fills my needs. If there are specific states you need a permit for list the states and someone will suggest the correct permits you'll need.
Click on SC first to establish your resident permit, then click on other states that you are thinking of getting a non-resident permit in. The map will then show you which states you would be legal in based on state-to-state reciprocity.
Your SC and NH permits will allow you to carry in about 31 states already!
Please note that laws vary widely from state to state, and it is not enough to have a permit in a state in order to safely carry there. You must also know that state's laws about carrying there. For example, some states will not permit you to carry your weapon in any establishment that serves alcohol, including restaurants that have a bar. Others prohibit carrying on the grounds of any establishment used for education. Research the state you are going to visit before going there.