Could you please tell me the precise meaning of "appropriate" and "substantiality" in this excerpt from the chapter six of The Great Gatsby by F. Scott Fitzgerald?
"He was left with his singularly appropriate education; the vague contour of Jay Gatsby had filled out to the substantiality of a man."
In The Great Gatsby, by F. Scott Fitzgerald, Jimmy Gatz transformed himself into Jay Gatsby when he was seventeen years old. His life changed when he met Dan Cody and traveled with him for five years on a yacht. Cody was rich, hard-living man, and he trusted the young Gatsby to keep him from doing anything too outrageous.
In the passage you mention, Gatsby has just learned his first significant hard lesson in life.
[I]t was from Cody that he inherited money--a legacy of twenty-five thousand dollars. He didn't get it. He never understood the legal device that was used against him, but what remained of the millions went intact to Ella Kaye [a gold-digger who manipulated Cody and got all his money]. He was left with his singularly appropriate education; the vague contour of Jay Gatsby had filled out to the substantiality of a man.
The two words you mention are used in this passage much as they are typically used elsewhere. Appropriate means "suitable for a particular person, condition, occasion, or place; fitting." In this case, Gatsby thought he was going to get an inheritance but did not; this is a particularly suitable ("singularly appropriate") lesson for him to learn at this stage of his life, for it is a pattern which will repeat itself many times. As he matures, he will lose things he desperately wants, and perhaps feels entitled to--including Daisy, twice. Sometimes it will happen and he will not even really understand why, just like his lost inheritance.
This experience of losing something he wanted, without really understanding why it happened, caused Gatsby to grow up even more quickly than the rest of his experiences since he left home had done. In fact, it is this experience, this loss, which completed his transformation from boy to man. The word substantiality here can have several shades of meaning.
Substantiality means "true or real; not imaginary." Until this incident, Jimmy Gatz had been playing the role of Jay Gatsby; now the transformation is complete, and he is fully Jay Gatsby--for real. Substantiality also means "solidly built; strong." The boy-turned-man is stronger for having experienced this loss; Gatsby will need that strength to persevere in his romantic quest for Daisy.
Ironically, a third meaning of substantiality is "possessing wealth or property; well-to-do." Though this particular meaning of the word does not describe Gatsby yet, it soon will.