How we cite our quotes:
"Let's start right," she interrupted herself suddenly. "Who are you, anyhow?"
For a moment, Dexter hesitated. Then:
"I'm nobody," he announced. "My career is largely a matter of futures." (3.14-16)
Dexter has already made plenty of money in the big city next to Black Bear Village. But he still thinks of his career as "a matter of futures." This is a bit of a pun: futures trading is when you try to make money by gambling on changing commodity prices. But Dexter's career is also literally a matter of futures: he wants to make himself into something new. He wants to join Judy's wealthy social world of country clubs and servants. He is not there yet, but he is taking steps to make sure that he will, one day, be somebody in upper class society. Until he reaches that stage, though, he is "nobody." Looks like his entire identity is bound up with his ambition.
The dream was gone. Something had been taken from him. In a sort of panic he pushed the palms of his hands into his eyes and tried to bring up a picture of the waters lapping on Sherry Island and the moonlit veranda, and gingham on the golf-links and the dry sun and the gold color of her neck's soft down. And her mouth damp to his kisses and her eyes plaintive with melancholy and her freshness like new fine linen in the morning. Why, these things were no longer in the world! They had existed and they existed no longer. (6.34)
Dexter loves "the glittering things themselves" (2.1). He doesn't just want money; he wants the beautiful life that he has always imagined belongs to the rich. And now, he finds that even the lives of the rich are disappointing (Kim Kardashian teaches us that lesson, too). There is no truly romantic or perfect experience, regardless of which class you belong to. All of Dexter's ambition suddenly appears hollow and pointless. Thanks for the upper, Fitzgerald.