Area of influence research and buildings determine how far away from your own territory you can establish trade routes. As you research them you will find you can build trade routes further and further away. Usually the campaign maps fog of war is moved back as you complete the research/building.

You also need to research various trade items before you can build trade routes on land or at sea. Once done the you can start creating trade routes and increase the amount of gold you have available each turn.

You can build trade routes on land by selecting an neutral or friendly capital and clicking on the building menu in the normal way. Any available Trade Buildings will appear on the list. Just build them as if you where improving your own regions. For sea trade routes you need a Merchant Harbor, once built you will be able to access any Merchant vessels available to build in that region by clicking on the trade routes tab. The Build units icon will then change to show only trade vessel units instead of naval or army units. Any ship you build whilst the trade route icon is selected (so the trade routes show on the campaign map) will then appear in at sea in the region that built it. You will get a message that its built usually. To see it just click on the trade route icon again.

Select the merchant vessel and some neutral or friendly ports will appear to have a green ring around them. Drag and Drop the Merchant vessel over the Port to create a sea trade route. The trade route will turn from gray to green once you have done this. When the ship is over the port, it usually goes slightly brighter so you know is you drop the ship there, it will create the trade route, if it does not change colour it means you do not have your mouse pointer over the port.

As you conquer more capitals you will find your gold drops and you start to become short on cash. About the time this happens a new set of buildings for raising taxes in side your empire starts to take over from the Trade buildings. These should be consider a natural progression from the Trade buildings designed to keep the gold flowing in the late game.

Written by giskard