In The Great Gatsby, how are East Egg and West Egg symbolic?
East Egg stands for the established wealth accrued over generations, or, "old money." It is the home to Daisy and Tom Buchannan, and other very wealthy families of notoriety. The people who live here have been born into wealth, and have married into wealth. Before Daisy married Tom, she was not a poor girl by anymeans; in fact, both she and her best friend, Jordan, were aristocrats from Louisville before she married Tom and moved to New York.
West Egg, conversely, stands for the "new money", or, group of people have recently acquired a great sum of money and are trying to fit into the lifestyle of the rich and famous. They are not respected as equals by their counterparts on East Egg. This is home to Gatsby and Nick in the story. Nick rents a small cottage there for a modest price, while Gatsby has an enormous mansion for entertaining guests and attracting Daisy's attention.
If East Egg represents those who have always been wealthy and already have the dream, then West Egg must represent those who have recently found the means (legal or illegal) to buy their dreams and flatter those around them.