Mitchell means wealth; the novel means the dream-ideal. That it even admits the
possibility of "good" is somewhat surprising, and brings us back to
the argument between Antonia and Decoud, in which Antonia defended idealism as
the fount of great human qualities.
In Mitchell's line the key word is "and" (where we might expect "or");
i.e., in the human story of ideals and power there can be no good without evil.