In Charles Dickens' Great Expectations, the story's protagonist and narrator, Pip, aspires to far more than his humble beginnings would suggest might be within his reach. It his encounters with the doomed escaped convict and with the reclusive Miss Havisham, however, that sets him on a path entirely at variance with his initial expectations. Not for nothing did Dickens title this story Great Expectations, as Pip would prove far more ambitious than his kindly brother-in-law Joe would have anticipated, and it is only thanks to the peculiar role of the escaped convict, Abel Magwitch, who proves to be Pip's benefactor, that the young man can hope to pursue the better life he comes to believe he deserves. Pip knows, however, that the path to prosperity does not lie in a future as a blacksmith, the profession of his brother-in-law, in whose poverty Pip has been raised.
This, then, is the context in which Pip discusses the money he as been given by Miss Havisham, background relayed through his discussions of his plans with Biddy, the girl who has moved in with Joe, Pip's sister, and himself. Pip, as part of his now-regular visits to Miss Havisham on the occasion of his birthday, is given by the elderly woman a "guinea" In Chapter 17 of Great Expectations, Pip mentions that he has noticed a change in Biddy:
"It came of my lifting up my own eyes from a task I was poring at - writing some passages from a book, to improve myself . . ."
This seemingly innocuous passage means nothing until, as he continues his conversation with Biddy, Pip reveals to what purpose he has been spending the money he receives from Miss Havisham:
"How do you manage, Biddy,’ said I, ‘to learn everything that I learn, and always to keep up with me?’ I was beginning to be rather vain of my knowledge, for I spent my birthday guineas on it, and set aside the greater part of my pocket-money for similar investment; though I have no doubt, now, that the little I knew was extremely dear at the price."
The answer to the question -- on what does Pip spend his money in Chapter 17 -- is books. Pip, dissatisfied with his lot in life ("‘Biddy,’ I exclaimed, impatiently, ‘I am not at all happy as I am. I am disgusted with my calling and with my life'"), has been spending his money on books with which to enrich himself intellectually -- a key, he believes, to upward mobility. Pip's frustration has become palpable, and his ambitions for a more materialistic existence drive him to pursue self-education as a means to his ends.