Any ideas for my novel's plot?

So I've got two story lines to my plot sort of done but I need help with the main storyline for the narrator.

One element will be the narrator's little brother's experience dating in high school, out of race, and the issues he encounters with people's negative views of the relationship.

The other element is the narrator's subconscious/unaware, subtle attraction to his coworker, who is dating, quite simply, a douchebag. They are good friends, though, throughout the novel.

I want the ending of the novel to be that the narrator realizes he wanted the coworker all along but throughout the novel he has been doing things that signal his want, but he was unaware of his attraction. What could he possibly do? I thought maybe he could be settling for a below average looking girl and everyone looks down on him because of this, but then I'm lost on the rest of the idea. And if it helps, I want this plot to resemble the style of writing in Great Gatsby, not necessarily the story, but the style. Thanks in advance.