Nick Carraway, the novel's narrator and protagonist, begins The Great Gatsby by recounting a bit of advice his father taught him: don't criticize others, because most people have not enjoyed the "advantages" that he has. Nick says that as a result of following this advice, he's become a tolerant and forgiving person who resists making quick judgments of others.
Nick's "advantages" come from "old money." Nick casts himself as someone who doesn't judge based on class, which indicates that other people do judge based on class.
For instance, Nick says that though he scorns everything Gatsby stood for, he withholds judgment entirely regarding him. Nick says Gatsby was a man of "gorgeous" personality and boundless hope. Nick views Gatsby as a victim, a man who fell prey to the "foul dust" that corrupted his dreams.
Nick introduces Gatsby and connects him to both new money and the American Dream, and indicates that Gatsby was done in by the "foul dust" of the Roaring Twenties.
In the summer of 1922, Nick, a Yale graduate, moves from his hometown in Minnesota, where his family has lived for three generations, to live and work in New York. He has recently returned from military service in World War I, an experience that left him feeling restless in the dull Midwest.
As a Yale graduate, Nick clearly comes from old money. His wealthy heritage has been closely tied to one place, but WW I and the 1920s upset that old order.
Nick intends to become a bond salesman, a line of work he says that almost everyone he knew was entering. Nick hopes to find a taste of the excitement and sense of possibility that was sweeping the nation in the early 1920s. He says moving to New York offered him and everyone else the chance to discover or reinvent themselves.
The 1920s boom turns the American Dream on its head. Instead of going west to build a fortune and a life, people in the 20s abandoned their roots to come east for the chance at fortune.
Nick rents a house in West Egg, a Long Island suburb located directly across a bay from East Egg. Nick observes that the two communities differed greatly in every way but shape and size. West Egg is where the "new rich" live, people who have made their fortunes only recently and have neither the social connections nor the cultural refinement to be accepted among the "old money" families of East Egg.
"Old money" East Egg faces "new money" West Egg across the water, symbolically showing the class rivalry: the towns literally oppose each other. That "old money" Nick rents a house in "new money" West Egg shows he spans both worlds.
The West Egg "new rich" are characterized by garish displays of wealth that the old money families find distasteful. For instance, Nick's small house sits next to an "eyesore" of a mansion owned by Gatsby, a man Nick knows only by name. Gatsby's mansion is a gigantic reproduction of a French hotel, covered in ivy and surrounded by forty acres of lush lawns and gardens.
Gatsby's mansion represents the "new money" class, which overcompensates for its lack of social connections through lavish displays of wealth. The "old money" class considers this tacky, proof of their superiority to "new money."
The main story begins when Nick, who, though he lives in West Egg has East Egg connections, drives over to East Egg to have dinner at the Buchanans. Daisy Buchanan is Nick's cousin, and Nick vaguely knew her husband Tom because Tom also attended Yale. When Nick arrives, Tom is dressed in riding clothes. Tom speaks to Nick politely but condescendingly. Nick remembers that plenty of people hated Tom at Yale, and notes that both Tom's arrogance and imposing stature have changed little since those days.
Tom's riding clothes identify him as a member of the "old money" class: horseback riding was a hobby only of the rich who had great country estates. The more urban "new money" wouldn't ride horses. Yet Tom's stately riding clothes can't hide his hulking body, just as his politeness can't hide that he's a jerk.
At dinner Nick meets Jordan Baker, a young professional golfer, who is beautiful but also seems constantly bored by her surroundings.
Jordan's world-weary boredom shows the emptiness of "old money."
Soon, Tom launches into a diatribe about the downfall of civilization as described in a book entitled The Rise of the Colored Empires. The book explains that the Nordic race, with which Tom identifies himself, created civilization and is now threatened by the rise of other, inferior races. Tom urges everyone to read the book. Daisy tries to make light of his suggestion.
Tom's outburst shows that old money is insecure about the rise of new money, which makes old money feel as if the world was falling apart. Old money is also hypocritical, hiding hatred and corruption behind a veneer of taste and manners.
Just then, Tom learns he has a phone call and leaves the room. Daisy follows quickly behind, and Jordan tells Nick that the call is from Tom's mistress. The rest of dinner is awkward. As Nick is leaving, Daisy and Tom suggest he think about striking up a romance with Jordan.
While Tom shows off his house and family and manners, he has a mistress on the side. Hypocrisy and rot are at the heart of old money in the 1920s boom.
Upon returning from dinner, Nick sees Jay Gatsby standing on his lawn and gazing out across Long Island sound. Nick considers calling out to Gatsby, but stops himself when he sees Gatsby extend his arms out toward the far side of the water. Nick looks across the water and sees only a tiny green light blinking at the end of a dock.
Gatsby's gesture is symbolic of his character: he is a hopeful seeker of unattainable dreams. It's not clear at this point what the green light symbolizes, but it's clear that to Gatsby it symbolizes some dream or hope.