This story is specific to opulence in the early 1920’s and how corruption and obsession can ultimately ruin not only one person but many including dynasties. It is important to completely understand this idea as you begin to write. All characters are flawed in this story, whether rich or poor, whether intentional or not they all admire, participate or become the corruption and in that the demise of the characters is a far-gone conclusion, however, the secret of Gatsby is what keeps this story and its first-person narration propelling forward.
Who is the character?
What is their journey? – use the Hero’s Journey to detail and complete the information.
What is their role in the story? Are they the protagonist? antagonist?
What is your character’s outcomes? Do they succeed? Do they fail? How is that structurally important to the outcomes in the story?
What is their biases? Do these biases play out in the outcome of the story?