Only F. Scott Fitzgerald himself can answer this question with any certainty at all. According to the forward of Scribner's The Great Gatsby, Fitzgerald desired his novel to be "a consciously artistic achievement," which suggests that Fitgerald's purpose in writing The Great Gatsby was to create a work of art.

Fitzgerald wrote many letters to his friends and editors, and in this correspondence, Fitzgerald reveals what he may have meant by an artistic achievement. He writes in some of his letters of how long it took him to write the novel (about one year), and in others, he claims that everything he had left out of The Great Gatsby would be enough to create another book entirely. The dedication and the restraint that Fitzgerald must have practiced to create the book is representative of successful artists of all types; as a writer, Fitzgerald set his vision down in words, and the artistry is evident in the book's great beauty and enduring popularity.

Ultimately, we cannot determine the answer to this as it would require being able to see inside the mind of Fitzgerald and assess his inner feelings and motives, something that is not possible. 

We do know that Fitzgerald, starting as a teenager, longed for literary success, wanting both to create great works and to become well-known and well-respected. Part of this may have stemmed from his family background, which existed at the fringes of the elite society of Minneapolis; as a student a Princeton Fitzgerald also found himself on the margins of an east coast elite. He was strongly ambivalent about the elites he both wished to join and despised for their insularity, materialism, and self-centeredness. Thus to some degree we can assume that among Fitzgerald's motives was a desire to work out some of his own ambivalence to upper class society.

Finally, Fitzgerald was a professional writer who was attempting to earn a living by writing and who was motivated in part to write because it was how he supported himself and his wife Zelda.  

What is the function of the symbolism in The Great Gatsby?

From the pessimistic angle, "The Great Gatsby" is a satire of The American Dream.  Daisy, always dressed in white with a white roadster is blank and transparent--ethereal like the age-- becoming whatever one perceives her as.  After her husband discovers her telling Gatsby "I love her," he looks at his wife "as someone he knew a long time ago."  The remark that Daisy's voice "is full of money" comes from Gatsby, for that is his perception of his "golden girl," Daisy.  And, because of this perception, Gatsby believes that he must win Daisy with his wealth.  This wealth, then, is equated with the American Dream, a dream that turns false with Gatsby becomeing a truly tragic figure.

The overwhelming materialism of the era is clearly satirized by Fitzgerald as he describes the decadence of the people--the "twins in yellow dresses"--attending the parties of Gatsby.  His car is, indeed, symbolic of the love of materialism and the conferring of power to the acquisition of such material things with its fenders like wings and

a labyrinth of windshields that mirrored a dozen suns....bright with nickel.

Such symbols remind the reader of the excesses of the 1920s, the shallowness of the people who sought only material possessions and money as their goals and the disillusionment that follows.

What is the function of the symbolism in The Great Gatsby?

Symbolism allows the novel to be read with multiple perspectives.

First, it can be read by a feminist angle: women are characterized as symbols, objects of men, temptresses, and materialistic gold diggers.  They are "hopeless little fools" whose voices are "full of money" but they don't say anything.  They are careless (Jordan), careless drivers (Daisy), careless lovers (Myrtle).

Second, the novel can be read by Marxist critics.  Look how social classes are depicted in the novel: there's the elite East Eggers (the bourgeoisie) from the established East Coast, the West Eggers from the west, and the Valley of Ashes (the proletariat) caught in the middle.  Nick, the narrator, is from the Midwest; though he's from the proletariat he likes the fact that Gatsby has joined the bourgeoisie despite his criminal means to the end.  There's a definite Midwestern bias in his narration, and all the symbols are colored accordingly.

Third, the novel can be read by Jungian myth critics who see the same symbolic stories in Gatsby that have been told throughout history.  Daisy is a siren to Gatsby's Odysseus.  Nick is a Nicodemus to Gatsby's Jesus.  Gatsby is a Bryonic hero whose desires are so focused that he doesn't see his death coming.

Of course there's the color, clothing, and geographical imagery.  Fitzgerald uses heavy symbolism and metaphor to allow the novel to transcend time, to be a quintessentially optimistic and pessimistic American novel.  In Gatsby, America is both full of dreams and false promises, depending on where you live, who you are married to, and what kind of car you drive.

What is Fitzgerald's purpose for creating symbols in The Great Gatsby?

Well, the purpose of symbolism in any literary form is to elevate the everyday to the status of art. Symbols evoke meaning beyond the usual, literal meaning. Symbolism simply (and reductively) makes things more complex and interesting! How much more compelling is it to understand, for example, that the "green light" on Daisy's dock is symbolic of the "green light" she seems to give Jay, and how the symbol of the lake is akin to the distance between the two of them?

If you have specific questions about other elements in "Gatsby" that you think may be symbolic, please let me know.

What is the point of studying symbolism in The Great Gatsby?

It is important to remember that literary fiction is an art form. Symbolism is a tool that helps a writer to establish their style; handled well, it adds much to a work's aesthetic value. F. Scott Fitzgerald is famed not only for his lyrical prose, but also for his skill in weaving symbolic motifs throughout his work, such as in The Great Gatsby.

Fitzgerald uses color symbolism to great effect in the novel. White is Daisy's signature color; it surrounds her in her home, her car when Gatsby first meets her, and her clothing. It is used ironically to suggest that she is far from what the color usually symbolizes: purity or innocence. Green is associated with Gatsby: the jersey he wears as a young man working the Great Lakes, the leather interior of his opulent Rolls Royce convertible, and the color of the light at the end of his beloved's dock and the symbol for his dream.

The names that Fitzgerald chose for his characters also have symbolic elements. Daisies are winsome flowers with white petals whereas myrtle is a hardy, evergreen shrub, and it seems likely that the contrast is meant to be somewhat humorous. Cars of the 1920s included a Jordan and a Baker; one was sporty while the other was more conservative, as if to suggest a paradox within the character.

Symbolism in the hands of Fitzgerald becomes a writer's tool that adds style, deepens meaning, and aids in characterization.