The school symbolism
The setting of the story has embedded symbolism in it that helps to show Will and Andrea's competition in a specific way. They are not just competing with their skills; they are also actively learning how to defeat the efforts of the other one. Together, they each hypnotize Brandt with their personality, Andrea luring him toward romance, and Will luring him toward fraternal competition. The symbolism of the school underscores the hypothetical nature of this competition, because they are not conning real adults in full-blown business ponzi schemes—they are just being nefarious youths.
The male and female foils
Foils tend to be the same gender because that is a helpful reminder to consider foils. But in this book, the non-romantic, Platonic acquaintanceship between Will and Andrea is a stage for foiling, because they are literally attempting to foil one another's plans, and also because they are literally character foils. They have almost everything in common, which makes them hate each other. What is worse is that they each have unique strategies for conning dumb rich kids that drive them naturally to compete with one another. It is a true battle of the sexes because of this foil.
The boon
Will and Andrea up the ante in their agreement. Whoever can con a rich kid out of $50,000 gets to be crowned as deceitful king or queen of the school, and in addition to that boon, the losing student must leave the school forever. The boon is a symbol for pride and competition. This is an ironic symbolism, because in direct conflict, they would do war against each other for the boon each other possessed, but in this book, they are competing for a boon that belongs to neither of them. This is an honor battle between people without integrity, but the reader enjoys rooting for them both anyway.
Gatsby as an allusion
When F. Scott Fitzgerald wrote The Great Gatsby, he managed to create an archetype. Gatsby symbolizes the absolute convergence of greed and approval. Because of greed, Gatsby acted unethically to obtain money so that he could earn the approval of his true love. When Will falls for a girl named Gatsby, that exact dilemma re-emerges in a brand new context. Can Will still impress the girl while so distracted by all his business schemes?
The trickster motif
The allegorical value of this story is that these students have abandoned integrity for trickery. This makes them like Ulysses of Classical folklore. As tricksters, they are constantly balancing positive and negative outcomes, and they run the serious risk of exile and rejection from community. That is what is so symbolic about the stakes of this competition. Tricksters hate to be separated from community because it is within the garb of local community that they are able to manufacture plans by manipulating the trust of people they see often.