First of all, the situation itself shows the American Dream. In this apartment, average people who are working to raise their station in life meet together and talk as if they are wealthy, carefree people. They complain of their stations, they talk idle of vacations, and they gossip of others. Moving beyond the situation itself, the conversations reveal much about the American Dream. We see Myrtle's discontentment with Wilson. We hear that Tom is discontented with Daisy. We also see the lies that help foster a superficial relationship, such as Tom lying about Daisy being Catholic.
In this scene Fitzgerald is able to show his perspective on the American Dream. The American Dream is the idea that anyone can make anything of themselves. However, Fitzgerald shows the disillusionment with this idea that many of his contemporaries shared. Rather than bringing out the best in people as they work to improve themselves, Fitzgerald shows the superficiality and shallowness of this time.