Just the box and an antenna. If you have new boxes from DirecTV you will need to ensure you don't bring the Genie (HR34/44) or the H25 (small profile receiver) as they need special treatment.
Otherwise, you need to determine a budget and compare that to how much work you want to do. There are a variety of antennas from manual tripod mounted antenna, semi-automatic and fully automatic portable dome style antennas and fully automatic portable and roof mounted units. The more work the antenna does for you the more expensive it is.