How did Mesopotamia cope with a lack of resources

Make do with what you have. The Mesopotamians gave us a very valuable building material the brick. Having no locally available stone they used the plentiful supplies of mud and clay found on the banks of the Euphrates to make bricks. There is also trade, exchange what you have for what you lack. In their case it was agricultural produce. This is how Babylon became a thriving and powerful city. Finally when you finally become more powerful take the resources from your neighbours by force.