In terms of the American Dream, Gatsby is literally and figuratively the self-made man. He remakes his entire identity in pursuit of one dream: Daisy. He uses his personal skills and street smarts to obtain a significant degree of social standing via obtaining a large amount of wealth. His methods of getting there are not entirely ethical: involved in drug trafficking or alcohol during Prohibition. But it's almost easy to look past this because Gatsby is essentially the same young, naive man who was in love with Daisy. He uses wealth to keep his dream of reuniting with Daisy alive: keeping a kind of vigil over the Green Light until he's ready. So, tying in time with his dream, which he pursues by living an extravagant lifestyle, Gatsby is sort of stuck in the past, but living in the present. His dream is timeless. Unfortunately, the rest of the world, including Daisy, has moved on.