Please explain the theme of waste in "The Great Gatsby". Fitzgerald conveys this not only through the narrative, but also with literary devices.
There is waste because there is excess. The story is largely about the excesses of the rich. They spend days drinking and smoking at parties. There is nothing real in thier lives.
Lets start with the literary devices. The symbolism of "waste" in this story is the wasteland between Long Island and New York City. It is the heap of ashes that lies beside the train track, looked over by the billboard of Dr. Eckleburg's eyes.
This is a valley of ashes--a fantastic farm where ashes grow like wheat into ridges and hills and grotesque gardens where ashes take the forms of houses and chimneys and rising smoke and finally, with a transcendent effort, of men who move dimly and already crumbling through the powdery air.
This description provides a negative view of industrialization, showing the effects of it. Gatsby's parties are another example of waste. The excessive food and drink are for show; they are being wasted on people who do not need them and for a purpose that is devious in nature - to catch the attention of a married woman.
This literal waste connects to the waste in the lives of the characters. Gatsby has wasted time and money on a woman who is not available. His senseless death is also waste. Tom and Daisy waste their lives, living in a loveless marriage and doing nothing of use. They party, they argue, they commit adultery, they discrimate against those of lower class. They produce nothing useful nor do any constructive work. Fitzgerald was showing a society that had become morally wasteful, rich but unproductive, and ultimately doomed to destruction - like the valley.