Money in the Great Gatsby is what got most of the characters where they are in their lives. Specifically for Daisy, she based her choice of a husband off his money. She liked Gatsby as a soldier, but obviously didn't love him enough to say No to Tom's later proposal. Daisy understands that her place in 20's society can only be found by how much money her husband possesses, she adopts this mentality and that is why it was said her voice is like money.
Gatsby throughout the novel and his obsession with Daisy uses money to try and continuously win her favor. He throws the elaborate parties and buys the most elaborate things in the hopes of attracting her and "winning her back"
from Tom. Fitzgerald's motif of money is meant to demonstrate that while the characters have more money than they know what to do with, and throughout the book it looks like they're having loads of fun with all their purchases and parties, at their core they're immoral and selfish people who have fallen victim to their illusions of money and success. Money makes the characters have great amounts of material value but in the end robs them of any morals and true happiness they could hope to achieve. The greatest example of this is the lack of people who attend Gatsby's funeral. It proves that people only had an attraction to money in the story, rather than the character of Gatsby himself.
