What is a quote from the book when Bilbo is talking, and what does it show about who he is?

Do you mean any quote?

"It will not be long now," thought Bilbo, "before the goblins win the Gate, and we are all slaughtered or driven down and captured. Really it is enough to make one weep, after all one has gone through. I would rather old Smaug had been left with all the wretched treasure..."ch 17

Bilbo is realizing the toll that war takes on everybody. He sees how the "wretched treasure" costs lives and peace. Bilbo has matured from being a naieve Hobbit to a Hobbit who understands that greed and unabashed desire ruins life.