Midsummer Reveler is a three item set that is worn in the chest, shoulder, and feet slots. These items are available for purchase using during the Midsummer Fire Festival event. Note the shoulders can be sold back within 2 hours (like a tier set piece), which allows purchasing them, completing the dance, and then sell back to buy a pet.
This set does not give any set bonus. However, you must have the complete set to be able to complete the achievement .