Gift sets are special building items periodically placed in the "Available Gifts" area by Playdom. Once placed in the available GIFTS area, they become available for players to gift to one another. Collection of these "Special Items" over a period of five consecutive days will allow the player to claim a special "GRAND PRIZE GIFT ITEM". This grand prize item,(in addition to happiness} will give you additional benefits for your city such as permanent overall attack or defense boosts.
Players obtain these items by receiving them as gifts from fellow allies. They can either ask fellow allies to gift them these special items or they can send them to another ally, hoping that the ally returns the same item as a gift to them.
Players must collect from fellow players all five of these special items over a period of five days. On the fifth day, if a player successfully has collected all five Gift Items, they will be awarded a final "Grand Prize Gift Item". It's this final item that gives your city the special "boost".
If a player misses one of the "special daily items" or fails to receive one as a gift, they may obtain the missed item by clicking on the "RAFFLE" button. There is a 1 gold charge to play the "Raffle". And, as the name suggests, the item you gain from the raffle MAY or MAY NOT be the item you are missing. So the missed item COULD end up costing you more than just 1 gold to obtain it.
Once the player has collected all five special items, they go to the Gift Sets tab where they will be given the opportunity to "REDEEM" the "Grand Prize Gift Item".