What does the novel has to say about the condition of the American dream in the 1920s?

The noveau riche that populate Gatsby's parties are the epitome of the vapid pursuit of material wealth. Despite the opulence and grandeur of Gatsby's legendary swarays, nobody seems particularly happy. This goes for Gatsby as well. He sits alone like a third person watching and pining after a girl (Daisy) that is more illusion than anything else. This was supposed to be the American Dream but underneath it was rotten to its core. The American dream was based on financial speculation and dreams rather than hard work and financial prudence. This will all come tumbling down during the Great Depression.