The name of the game is goods, so get your hands on them as quickly as you can. Each city you hold enables you to draw a card which is hopefully a 'good' of some kind. Sometimes disasters are drawn, but crafty players can pawn them off to an unsuspecting empire willing to trade. If you have the minimum number of goods to be able to trade, you join the other empires in a round or two of bartering. This process can be confusing, and takes some practice to acquire a profitable trade, especially since the computer players tend to shy away from trading with a human opponent.
Goods are more valuable in quantity, since their value is multiplied by the number held.
However, you don't always know what you are getting. One of the three goods you receive could be a bluff, being a good of lower value, or even a disaster. The value of the goods are used to buy 'advances', referred to as tools. These tools include items such as agriculture, medicine, literacy, etc. Each tool obtained gives credit towards the purchase of future tools, and may provide relief from one of the various disasters should one befall you.