Danny is much more realistic than Gatsby. Gatsby is essentially trying to relive the past. He will do anything to get back together with Daisy. In his idealistic determination to win Daisy back, Gatsby willing involves himself in bootlegging and gambling, anything to put himself in a higher social position because this puts him closer to Daisy's social circle.
Danny does befriend Judge Smails in attempts to win the Caddy scholarship but in the end, he decides his integrity is more important than selling out to Judge Smails.
Danny and Gatsby (Gatz) are similar in that they both come from poor families. However, Gatsby is chasing an ideal memory of Daisy; he believes he is chasing love. Danny is simply trying to get a scholarship. Gatsby won't compromise his struggle to win Daisy back because, in his idealism, he thinks his project is righteous no matter what means he must go through to achieve the goal: love, surely a righteous goal. Danny, on the other hand, is just trying to get on equal footing with the rich classes of the country club. Recognizing that he is selling out, Danny decides that he would rather play for himself (thus representing the poor) than play for Smails (thus representing the rich).
Considering this comparison, Judge Smails is like a combination of Dany Cody and Meyer Wolfsheim. Gatz sees how he can benefit from Cody and he becomes Gatsby and never looks back.
It was James Gatz who had been loafing along the beach that afternoon in a torn green jersey and a pair of canvas pants, but it was already Jay Gatsby who borrowed a rowboat, pulled out to the Tuolomee, and informed Cody that a wind might catch him and break him up in half an hour.
Like Gatsby, Danny essentially became someone else when he tried to win favor with the Judge. But whereas Gatsby never went back to being Gatz, Danny eventually stopped faking his admiration for Judge Smails and all he represents.
In attempting to win the scholarship, Danny does take a Gatsby-esque approach, but when he refuses to sell out, he becomes more like Nick Carraway.