I'm not sure about the exact requirements for your poem. Does it have to have a certain meter? Should it rhyme? Be sure you know exactly what your poem needs. With that said, here are some ideas and tips:
- For a two-voice poem, you should have two different speakers. This can take various forms. You might have one speaker be Jay Gatsby himself, and the other speaker be the author, or anonymous speaker who is addressing Gatsby or commenting about him. You could also have two people (such as other characters from the book) engaged in dialogue about Gatsby. They might be arguing about whether he is a hero or not; whether he was right in pursuing his dreams so vigorously, etc.
- To incorporate the Roaring Twenties, it would help to have images from this time. The period is characterized by excess and over indulgence. Generally, people did what they wanted, they had fun, and didn't care about the consequences. These ideas should be evident in your poem. You might have one voice enjoying the time while another voice warns against it.
- For Gatsby's characteristics, it is important to highlight the fact that he is a dreamer. He goes after what he wants and does not take "no" for an answer. Gatsby lives his life with the intention that things will work out the way he wants them to; there is no alternative. This mindset should be clear in your poem.
- Again, the purpose of your poem could be to show Gatsby as a hero because he goes for what he wants, or it could be to show him as a fool because he wastes his life going after what he wants. In the end, your poem should have some kind of message or theme. Making a statement about the kind of man Gatsby was during this time of excess would be a good goal for your poem.
These are just a few suggestions. The beautiful thing about poetry is that you have many options and you can be creative with it!