Gatsby is a "one in a million" character in that he starts out with almost nothing and becomes a millionaire. At seventeen, Gatsby was "a clam digger and a salmon fisher" and would do any work that came his way which "brought him food and bed." By the time he is in his thirties, Gatsby is a millionaire and owns a mansion that Nick describes as "a colossal affair." He is thus a self-made millionaire, and self-made millionaires are indeed rather rare.
One negative interpretation of Gatsby, however, is that he is incredibly dishonest. He lies about inheriting his wealth, what he does for a living, what university he attended, and even his war record. Owl Eyes captures quite nicely Gatsby's dishonesty when he calls him a "regular Belasco." David Belasco was a theatrical producer famous for elaborate and realistic set designs. Gatsby is a "regular Belasco" in the sense that his entire life is just like an elaborate stage set. Gatsby's life is, in other words, an elaborate façade, with little substance behind it.
Another negative interpretation of Gatsby is that he is blinded by his obsessive love for Daisy. For example, at the end of the story Gatsby decides that he will take the blame for Myrtle's death. Daisy was driving his car when the car struck and killed Myrtle Wilson, but because Gatsby is so desperately in love with Daisy, he decides that he will take the blame. He tells Nick that Daisy was driving the car but that "of course I'll say I was." Ironically Gatsby is ultimately killed by this willingness to protect Daisy, as Myrtle's husband shoots Gatsby thinking that Gatsby is responsible for his wife's death.