In The Great Gatsby, Fitzgerald offers up commentary on a variety of themes -- justice, power, greed, betrayal, the American dream, and so on. Of all the themes, perhaps none is more well developed than that of social stratification.
Fitzgerald carefully sets up his novel into distinct social groups but, in the end, each group has its own problems to contend with, leaving a powerful reminder of what a precarious place the world really is. By creating distinct social classes old money, new money, and no money Fitzgerald sends strong messages about the elitism running throughout every strata of society.