The economy of the Babylonian Empire was based around trade and the barter system. As Babylon benefited greatly from the Tigris and Euphrates River via irrigation, excess food and goods from farming was plentiful. These surplus supplies were traded for the raw materials (copper, gold, wood) that Mesopotamia was lacking. These goods were then made into jewelry and other trinkets that could themselves be traded to others.
Being an empire also ensured that these trade routes were extensive, going from Anatolia (Turkey) to as far as India. The routes flourished as the trade goods allowed Babylon to build weapons to protect trade caravans from raiders. This ensured its longevity as the center of trade in the ancient world, well beyond the various highs and lows of Babylon, until the Mediterranean replaced it as the new trading hub.