What is revealed about Gatsby in the flashback about "James Gatz" in Chapters 5 and 6 of The Great Gatsby?

Several elements are revealed about Gatsby in the
detailing of his former life.  The most pressing of which is that Gatsby is an
embodiment of the American ideal of being able to create one's own impression and
definition of self.  Unlike other cultures where who one is is staunchly defined by
individual background and family name, Gatsby is able to create his own self through his
own will.  In contrast to his own meager and humble beginnings, Gatsby is created
through a confluence of a desire to reach an ideal form of social perfection and an
embrace of materialism as the means to achieve such a set of ends.  Through this
section, we learn that Gatsby's embrace of illegal and dangerous ends are not done out
of malice, but out of a sense of creation and desire for matching this ideal of
perfection.  When we see Gatsby not align himself with his parents, we see the rootless
component of American identity.  While freedom is present, roots and connection seem to
be the cost of such endeavors.  This results in one of two conditions.  Either freedom
allows a sense of definition and autonomy that allows Americans to be what they wish to
be.  Gatz wishes to be and becomes Gatsby.  Or the opposite side of this is that the
embrace and construction of a life founded on pure freedom creates a setting where there
is little connection or attachment.  The creation of identities is about as casual as
attending different parties each night and interacting with different people for little
amounts of time and moving on to the next interaction.  Contingency is seen as something
that can be both liberating and sad.