On the surface, Fitzgerald paints the picture that these people sought material wealth and fame as their means to happiness. What has made his work so powerful is the timelessness of this theme and the consequences of the idea.
First of all, America was founded on the values of hard work. We still preach to children in elementary schools that if they work hard they too can be the next president of the United States, or they can be very wealthy. However, during the 20s, people began looking for shortcuts to that ideal. These shortcuts proved to have dire consequences. For example, bootlegging became a highly profitable industry. Many people lost their lives in the competition for and distribution of alcohol. Because of prohibition, some people became wealthy by breaking the law. This was also an era of easily attainable credit. People began buying cars and homes on credit. The began to understand they could have whatever items they wanted without paying for them now, they could always pay later.
Fitzgerald particularly illustrates this by the way people attend Gatsby's parties. These parties were free and he lavishly shared all he had with his patrons. You may recall the expensive dress Gatsby purchased for a woman who ruined hers at a party. These people had the perspective at Gatsby's parties that it was all for fun and that they had nothing to lose. They wore their best clothes and flirted with the rich and famous. Sometimes, just rubbing shoulders with people like that made the average people feel more worth in themselves.
Today, people work on credit as much as possible. We do it so much so that we have created a failing economy much like that which put our country into a Great Depression. We also do things that satisfy right here and right now, much like Gatsby's parties. With Twitter and Facebook today, we are made to feel like we can get to know celebrities and participate in life with them.