Studied in class
I studied this book in my lit class in school..
we learned that the East Egg was supposed to symbolize the people who could trace their money back through their ancestors... These people have degenerated and are really lazy etc.. They don't have to work. Example, Daisy-- she doesn't do anything.. People of the East Egg look down on the West Egg.
The West Egg was supposed to symbolize the American Dream, Or, New money. It symbolized, growth, more money, and making a name for yourself.
I do like what you wrote though. The valley of Ashes fits in well.. but could you explain why it symbolizes corruption?