The social setting of a majority of the action in the novel is divided between a parsing of the upper class; between "new money" and "old money". Though some of the novel is concerned with George and Myrtle Wilson, people of modest means, the greater interest of the novel is in wealthy society.
The people of this social scene are often frivolous, dramatic, self-absorbed, drunk, destructive, bitter, competitive, resentful of one another, and prepared to have a good time.
These traits do not form a singular personality or present a representative average. Instead, they describe a moiling social world that is (or has been) corrupted by a sense of entitlement. Values are replaced by a vague sense that money equates to morality. As the action of the novel shows, this is a false confidence in the power of money to excuse and justify behavior.
The materialism of the East creates the tragedy of destruction, dishonesty, and fear.
We can see this in the way Daisy and Tom are initially introduced as well as in the scenes of Gatsby's parties. The rich and wealthy, isolated from the rest of society, content themselves with revels and squabbles that sometimes turn into high-stakes dramas such as the one featured in the novel.