Gold is an important resource that you obtain as hourly tribute from the people who live in the islands you free from BlackGuard slavery. You can use an upgraded Radar to find these islands, and you may also have to dip into your gold reserves to pay to reveal areas of particular interest. Keep in mind that the BlackGuard forces can reclaim islands you have freed, and they may build stronger encampments there, so it is important to monitor activity at all times.