Uncle Pumblechook is “little more than a stereotype of a snob who takes every opportunity to poke fun at Pip when he is poor or to befriend Pip when Pip has money” (enotes characters)
Uncle Publechook is a money-hungry, selfish and conceited man. Plutomania is a craving or obsession for money. To be pompous is to have a very high opinion of oneself. Pip is not allowed to call him uncle “under the severest penalties” (p. 19). At meals, Pumblechook is loud and dominates the conversation, to his host’s chagrin.
But, Uncle Pumblechook, who was omnipotent in that kitchen, wouldn't hear the word, wouldn't hear of the subject, imperiously waved it all away with his hand, and asked for hot gin-and-water. (p. 22)
Pumblechook also pretends to know Miss Havisham, and claims to have arranged Pip’s visit since they are all such good friends, which is a total lie. When Pip returns, he makes up all kinds of stories about his visit and Publechook clearly demonstrates that he is a conceited liar.
When Mrs. Joe asks Pip what she looks like, Pip responds that she is “very tall and dark” (p. 47).
Mr. Pumblechook winked assent; from which I at once inferred that he had never seen Miss Havisham, for she was nothing of the kind.
“Good!” said Mr. Pumblechook, conceitedly. (“This is the way to have him! We are beginning to hold our own, I think, Mum?”) (p. 47)
You do not have to look far for examples of Mr. Pumblechook being a plutomaniac or pompous. He demonstrates these behaviors throughout. His only interest in Pip is when he gets his fortune, and then he pretends to be responsible for it.
All page numbers are from the enotes pdf full text http://www.enotes.com/great-expectations-text
Definition of plutomania (http://dictionary.reference.com/browse/plutomania)
Definition of pompous http://dictionary.reference.com/browse/pompous