The Great Gatsby is set among wealthy, educated people, who have lots of leisure time and little concern about people who are not in their social milieu. Nobody’s concerned about politics or spiritual matters but everybody cares about how they are perceived socially.
Those who do come from other classes seek and envy the glamour and lifestyle that they see in the elite. Jay Gatsby, the protagonist, is able to attain a certain amount of wealth, but he cannot fake education or social behaviours that only come with "old money."
The novel’s two main locales, West Egg and East Egg, are distinguished also by class. East Egg represents "old money" while West Egg represents the nouveau riche. East Eggers consistently look down on West Eggers for precisely this fact. Class and wealth are virtually indistinguishable from each other, but if a person lacks education, then he is clearly not part of the upper echelon.
The first and most obvious group Fitzgerald attacks is, of course, the rich. However, for Fitzgerald (and certainly his characters), placing the rich all in one group together would be a great mistake. For many of those of modest means, the rich seem to be unified by their money. However, Fitzgerald reveals this is not the case. In The Great Gatsby, Fitzgerald presents two distinct types of wealthy people. First, there are people like the Buchannans and Jordan Baker who were born into wealth. Their families have had money for many generations, hence they are "old money." As portrayed in the novel, the "old money" people don't have to work (they rarely, if ever, even speak about business arrangements) and they spend their time amusing themselves with whatever takes their fancy.
For the "old money" people, the fact that Gatsby (and countless other people like him in the 1920s) has only just recently acquired his money is reason enough to dislike him. In their way of thinking, he can't possibly have the same refinement, sensibility, and taste they have. Not...