Why are the settings so important? What do the different settings represent?
The settings are very important in this novel. They represent the different social classes and distinguish the traits of the different characters. Generally speaking, there are two sides: the east and the west. The west represents the hard working, ethical people. The east represents those who spend and consume without thought.
However, to be more specific, there are several important settings. Jay's house represents wealth not for the sake of spending selfishly, but for the sake of winning Daisy over. Daisy and Tom's house on the other hand is for show. They represent materialism and the lies and destruction that surround them.
The Valley of Ashes is interesting as well. That area and Wilson's garage represent what is discarded in our society. George was used and discarded, as was Myrtle. They were used for a little while, and then dumped or left to die. The Valley of Ashes is like that because it's the leftovers from the coal that is used in the city.
Nick's place on the other hand is very small, but big enough for one person to live in. His little house is sufficient. It's adequate, just like Nick. He doesn't use people, he doesn't destroy relationships, and he isn't wreckless. He represents the good in the story.