I am preparing an oral presentation explaining how, in F. Scott Fitzgerald's The Great Gatsby, Gatsby's obsession with fulfilling his ideal world (with Daisy) and his dissatisfaction with reality are what ultimately cause his loneliness. What are some good examples to use? How can one organize the arguments?
It is most definitely clear that F. Scott Fitzgerald characterizes Gatsby as being lonely due to his illusions of his life and dissatisfaction with his own life.
One place in the book in which this characterization is clear is towards the end of Chapter 1. Nick observes Gatsby come out of his mansion late at night and gaze towards the water. As he gazed, "He stretched out his arms toward the dark water in a curious way, and far as I was from him I could have sworn he was trembling." Nick turns to see what Gatsby is looking at and sees "nothing except a single green light" that was probably at the end of someone else's dock across the water. It is most likely Daisy's Dock, and Nick has just witnessed Gatsby giving way to his own grief due to his longings for Daisy. Gatsby deludes himself by dreaming he can one day win her back with his wealth and apparently, in his weakest grief-stricken moments, reaches out towards her dock as if he can pull her towards him.
Another place in which it is obvious he has only been deluding himself all these years is when Gatsby, Nick, Jordon, Daisy, and Tom all venture into Manhattan together to escape the heat. In the hotel, Gatsby and Tom start a heated argument. During the argument, Gatsby announces to Tom that Daisy doesn't love Tom, that she loves Gatsby instead. At first, Daisy agrees, but then Daisy says what Gatsby would never have imagined her saying: "Oh, you want too much! ... I did love him once--but I loved you too" (Ch. 7). At this point, Gatsby is forced to realize that all of his fantasizes of winning Daisy back were just that--fantasies and illusions, fantasies and illusions that have made him lonely all his life as he yearned for the impossible.
Based on the two examples given above, most likely, a chronological order will make the most sense for the order of your arguments in your oral presentation. By chronological, we simply mean organized on time the events take place, starting from first event moving to the last event.