When Gatsby takes Nick and Daisy to his mansion, he shows Daisy all his worldly treasures. In his bedroom, he shows her all of his shirts: “I’ve got a man in England who buys me clothes. He sends over a selection of things at the beginning of each season, spring and fall" (Ch. 5). He tosses the shirts to her, each one more elegant than the one before it. Daisy cries over them, saying that she's never seen such beautiful shirts before. However, it can be argued that she is crying over what she could have had: a life full of beautiful possessions with Gatsby.
Gatsby has been accumulating wealth and treasures to impress Daisy. He started out as a poor soldier, and works hard to earn his fortune. This emphasizes the idea of the American Dream: that you can build a successful life from poor beginnings. Gatsby puts emphasis on material possessions because he thinks that's what Daisy wants. A later quote, "Her voice is full of money," illustrates Gatsby's understanding that Daisy craves those finer things. The shirts in Chapter 5 are a symbol of Gatsby's need to show Daisy that he can take care of her and give her the things she wants.
The shirts reinforce the theme of love and money as intertwined. For Daisy and Gatsby, love is dependent on money and possessions.