Game has two types of attack troops, the squires and the knights.
The knights are squires converted into them when you get the rock upgrade and put coins on the shield, and the squire will go grab one of them in the side they are on.
So squire are the basic troops to attack, early in the game on second isle will be better (first isle you cannot attack, just leave).
Gather two squires that will be with three archers each, make them attack from one side putting coins on the edge of Kingdom flag and wait for it. You can help them to have a better time dropping coins from your mount ahead of the troops.
It will take more than usual for the squires and you will get it if one of them is kicked. Also be sure to drop coins on them so they can resist three rams from the greed