West Egg, where Jay Gatsby and Nick Carraway live, is for people with new money. They are looked down upon because they only came into wealth recently. People with old money, like Daisy and Tom Buchanan, live in East Egg. They are viewed as the upper class since their wealth has survived through generations. Daisy chose Tom Buchanan over Gatsby because of his wealth. Tom didn't work for his money like Gatsby did, which places him in the upper-class. The characters are only motivated to stay wealthy and keep their lavish lifestyle. In The Great Gatsby, wealth defines social class. This is proven by Tom Buchanan's established connections through old money. He is vain and constantly attempts to flaunt his fortune. Despite his extravagant parties, Gatsby will never achieve the status that Tom has because he has new wealth.
Jay Gatsby is not motivated by money. He uses wealth as a tool to impress Daisy in hopes that she would want to be in a relationship with him again. He spends his time and money throwing large, grandiose parties hoping it will catch her attention. Nick Carraway is also unconcerned about his wealth. He has enough money to live comfortably while enjoying the perks of having connections in the upper-class. Even though he has to work, his job in the bond business earns him high status.
[P1] People with old money live in East Egg. [P2] People with new money live in West Egg. [P3] People with old money have a higher social status. [P4] Social status is defined by wealth. [P5] Therefore, the theme of The Great Gatsby is wealth.