How is Tom Buchanan affected by materialism in The Great Gatsby?
Tom Buchanan, married to Daisy, is an Alpha Male and one to whom personal superiority is more important than ethics or morality. He uses his wealth and status to buy and bully respect; he cannot be argued with, because he will not listen to reason. To Tom, having wealth is less important than using it. He is contemptuous of Gatsby not because Gatsby is more successful than himself, but because he can't see that Gatsby is also buying respect, although for a different reason. For Tom, all that matters is being the most important person in the room, and spending money accomplishes that.
...Tom Buchanan of Chicago, with more pomp and circumstance than Louisville ever knew before. He came down with a hundred people in four private cars, and hired a whole floor of the Seelbach Hotel, and the day before the wedding he gave [Daisy] a string of pearls valued at three hundred and fifty thousand dollars.
(Fitzgerald, The Great Gatsby, mrbye.com)
Tom's materialism differs from Gatsby's in that he has no goal or purpose; he simply wants to be powerful. Tom believes that the accumulation of money is a means to an end; he is enabled in his cruelty because of his money, and he feels self-justified because the wealthy are an entitled class. In the end, Tom "wins" over Gatsby because he is more ruthless and without personal honor; he doesn't care about the innocent lives he has damaged, but only cares that he has successfully retained the only thing Gatsby truly finds important: Daisy.