There needs to be a ranking system in game. When attacking players there should be a damage percentage to let you know how much of the base is destroyed. You should get 1 star for 50% base destruction and 1 star when you destroy their temple and final star when full base is destroyed.
The amount of stars then could be given a set amount of points called battle points after each win. Such as maybe 50 pts if you only get 1 star, 300 pts for 2 stars, and then 3 stars you win 500 battle points.
You would also have to set battle points lost for each defeat you have defending base. Then you could hold like a weekly Olympic tournament for prizes for highest rank battle point players at the end of every week.