It let's you win Special Gangs Medals that give attack and defense. You also win Cash Bonus rewards based on the performance of your Gang. During some special tournaments you can also win Diamonds. At the end of the Tournament, Medals are awarded based on the ranking of the Gang in the tournament. Also, personal performance of each gang member can be seen in the Gang page. Based on the overall on you overall ranking in tournament special units are awarded to the top 20 players. A player's personal best ranking is shown on his/her profile.