Make sure you keep your armoury maintained so that you can build a boat capable of carring a large amount of soldiers to the island you are trying to dominate and overwhelm the oppostion with your forces.
If you are attacked and enemies overcome your defenses they will take your resources. This can be prevented by investing in a vault which will enable you to keep your gold and wood in it. Remember to strengthen the vault whenever you can as it takes damage over time.
Keep an eye on the Vault and Sawmil and upgrade these buildings whenever possible. These buildings are important because you lose the round if the Headquarters building is destroyed and the Sawmill is required to produce wood which is needed for most upgrades.
During the early stages of the game you will need wood to make most upgrades therefore it is important that you make Sawmill upgrades a priority each time they become available when you update your headquarters.