How is Nick affected by materialism in The Great Gatsby?
Although Nick aspires to the upper-class of the East Egg, he does not aspire to the ultra-materialism of the East Egg's Old Money class. Instead, he is trying to be an individual admired for his own hard work, not a part of the Old Money collective. Because of this, he is shown to be unaffected by most materialist attitudes; he is contrasted with Daisy, who is very materialistic and would probably have accepted Gatsby's offer if she had not already been married to a wealthy man. At one point, Gatsby offers Nick a part of his "side job" in bootlegging:
"...It wouldn't take up much of your time and you might pick up a nice bit of money. It happens to be a rather confidential sort of thing."
I realize now that under different circumstances that conversation might have been one of the crises of my life. But, because the offer was obviously and tactlessly for a service to be rendered, I had no choice except to cut him off there.
"I've got my hands full," I said. "I'm much obliged but I couldn't take on any more work."
(Fitzgerald, The Great Gatsby, mrbye.com)
While the offer would allow Nick to make more money than selling bonds, Nick doesn't see the attraction in simply gaining wealth and material goods. The immorality of bootlegging is more important in Nick's eyes than the respect he would gain from showing extravagant wealth; Gatsby deliberately chases that respect. Nick, therefore, represents a sort of uncorrupted ideal, a man who is more concerned with his inner honor than with the opinions of other people.