Hi Akin,
When many first read The Great Gatsby, they assume that Gatsby and Tom are in the same social class. But this is simply not true. Tom and Daisy Buchanan are of the true upper class. They live in the classy East Egg, with a large house, tons of money, nice car, and a cute daughter. They have even traveled the world together for many years. Their lives are a primary example of how the stereotypical upper class lives. But Gatsby's class is slightly different.
Gatsby is trying to pull a two-faced move on the reader. He appears to be the richest, most successful, and most popular man on the East Coast. But this is all a facade that he has built up. In reality, Gatsby is NOT rich at all. His mentor did leave him thousands of dollars, but his mentor's wife legally took the money before Gatsby ever got a cent. Instead, through sneaky and sketchy business deals, which included fixing the 1919 World Series, Gatsby gained money. He was originally born a poor farm boy, to uneducated and dull parents. Gatsby throws parties and has an extravagant house in order to be accepted by the upper class. The biggest difference between Tom and Gatsby is that Tom belongs in the upper class, while Gatsby is desperately trying to prove that he deserves to be in. The geography of the East and West Eggs show this division of class. The East Egg is where all the accepted upper class live. While Gatsby could certainly afford to live there, he doesn't, because he knows he doesn't truly belong. Gatsby instead lives in the less fashionable West Egg, which shows the clear division of the two classes: the upper class and the want-to-be's.