Characters in books can reveal the authors feeling toward the world. In The Great Gatsby, Fitzgerald suggested the moral decline of the period in America history through the interpersonal relationships among his characters. The book indicates the worthlessness of materialism, the futile quest of Myrtle and Gatsby, and how America's moral values had diminished. Despite his newly acquired fortune, Gatsby's monitory means could not afford his only true wish, therefore he cannot buy everything which is important to Daisy.
(Fitzgerald, -page 42-)
What you wish for is not always what you want or not all that glitters is gold. The wild lavishness of Gatsby's parties and the shallowness and purposelessness of the lives of the guests all kills Gatsby on the inside. All Gatsby wants when he chooses to be rich is to get Daisy. Daisy, who is wealthy and beautiful, symbolizes a way of life which is remote from Gatsby's and therefore more attractive because it is out of reach so he changes himself.
(Fitzgerald, -page 54-)
Myrtle and Gatsby both want to be part of the same elite crowd. They play a reflection of each other in the book by wanting the same thing but they have different methods of achieving it. Gatsby wants Daisy, and Myrtle just wants to be higher in society. Gatsby plays the god-like character in this book so his means are good but both him and Myrtle do bad things to get higher in a crowd that will never take them in. To make themselves appear better to the other crowd, they lose some of the moral fiber that was there to begin with.
(Fitzgerald, -page 83-)
Loss of morals in the 1920' in America caused the American dream to vanish. The god-like character of the book Gatsby, was a good person but he did bad things like bootlegging and joining in organized crime. Affairs happened in the elite crowd between Tom and Myrtle. Dishonesty reared its ugly head when Daisy killed Myrtle by running her over then blaming it on Gatsby. This causes the deaths of three people.
(Fitzgerald, -page 100-)
In summary, Gatsby struggled to gain acceptance among his social class and failed. He could not achieve the American dream or reach his dream for his true love. He changed himself into saying stuff like "old sport" and other stuff to make him be into impure. The complicated struggle for class distinction continued as his life was wasted.
(Fitzgerald, -page 122-)