How does Dickens use foil characters in Great Expectations to lead to theme of social class?

Foils are characters that are alike but different, used to
compare and contrast two characters.  Dickens loved to use foils, and he did so in many
of his novels.  One example of foils in Great Expectations is Pip
and Drummle.  Both are suitors for Estella.  Pip is a poor boy with a hard life. 
Drummle is rich and pampered.  Both are or are becoming "gentlemen" by Victorian
standards.  Drummle was born a gentleman, Pip has to learn to become
one.

In this novel, Dickens explores social class in many
ways.  Pip assumes that his life will be better once he has money.  So do his family and
friends.  Drummle has money and is absolutely miserable.  One of Dickens's favorite
themes is that money does not make you  a better person.  Drummle is not the better
person, and Pip starts to become as bad as Drummle.