Your Beachhead is the colored perimeter standing between your Haven and the sea. To purchase Defensive buildings, you need Rubies and Resources. There are two types of Defensive buildings: Fortifications (under the «Fortifications» tab on the «Construction» menu) and Improvements (under the «Improvements» tab on the «Construction» menu). Construction of some buildings is required to unlock certain new Naval Discoveries or more advanced Naval buildings. Each unit or set of units are produced at their own respective buildings. Your Naval buildings are where you recruit, manage, and develop all of your different fighting units. You start off with your Captain's Quarters already built - but you'll need to build a Market, Observatory, and Brethren Court before you can engage in any trade, discovery, or diplomacy. Your Command buildings are responsible for all the non-Naval functions that keep your Pirate Haven shipshape. You can purchase additional Rubies at the Bank by selecting the ""Bank"" button in the top right-hand corner of the screen.
Make sure you upgrade your Rum Cellar at the same rate at which you increase your Rum revenue or anything over your capacity will go to waste. The amount of Rum you can store in your Haven is limited by the capacity of your Rum Cellar(s). Build and upgrade your Rum Distilleries and the Windmill to increase Rum production. Rum is produced at your Rum Distilleries. Upgrade your Warehouse to store more Resources. The amount of Gold and Lumber you can store is limited by your Warehouse capacity. To gain more Resources, construct and upgrade Gold Mines and Lumber Yards and resource related buildings - such as the Goldsmith and Sawmill. You can make up for the discrepancy by trading Resources with other players. The ratio of resource fields varies for different Havens – some have more Gold Ore, others have more Stacks o' Lumber. The amount of Lumber and Gold you can gain per hour depends on the number of fields you have for these Resources, the number of Lumber Yards and Gold Mines you've build, and their upgrade levels. You need them to construct buildings, research Discoveries and produce new Units. There are three main types of Resources in the game – Rum, Lumber and Gold.
Resource Buildings are additions to your Haven that allow you to extract resources from your island, (or produce them more efficiently).
The same goes for several of the defensive Improvements that can only be installed on the Fortifications. For example, Fortifications can be constructed only on the Haven Beachhead sections. Some buildings can only be built on designated areas.