What is the symbolic value of money in the novel? What does it mean to different characters?
An answer to this question should point out that money is the be-all, end-all symbol to most of the novel's characters except perhaps Selden. The upper-class society depicted in the novel is built on money. Admission to society is based on money. Social acceptance and, more importantly, power are products of money. To Lily, money means the ability to gain a permanent footing in society; that is why she always wants more of it. To Selden, money is the means by which people are destroyed and false, meaningless societal relationships are formed. To Bertha, money is the means by which she can maintain her power and influence over other people in society, getting them to believe whatever she wants them to believe.
Does Lily change over the course of the novel? What motives her, and how do her motivations change?
A good answer would involve a discussion of Lily's continual motivation by money. Her basic motivation, the avoidance of "dinginess," never changes. Her goal is always to marry a wealthy man and live in the upper ranks of society. Her social stature is what really changes in the novel. As she falls lower into the "chasm" Wharton describes, her desire to get out becomes greater. Interestingly, this question could also be answered with a discussion of how Lily will never change her mind on some things, including her decision to repay Gus Trenor all his money even though she does not have to, and even though it spells her financial ruin.
What do you think it Lily's biggest flaw as a character? What is her "Achilles' heel"?
To answer this question, look at Lily's indecision. She holds firm to a constant belief that when it comes to marrying, she can always do better than the current situation offers her. This is why she delays in marring Gryce, Rosedale and Selden. Ironically, her standards never go up; they only go down as she becomes more desperate. Nevertheless, if Lily were not plagued by her wishy-washy nature, she would have gotten married earlier and most likely lived happily ever after. Her desire for more wealth and more fame (as also seen in her perpetual gambling) is what brings her down.