What lessons does Pip learn from his experience of becoming a wealthy gentleman?
In his moral regeneration of Stage III, learns the true meaning of the words of Mr. Jaggers, who has instructed Pip,
"Take nothing on its looks; take everything on evidence. There's no better rule."
Being a gentleman is not based upon appearances.
From his encounters with the cruel Estella and the exploitation of Miss Havisham, as well as his exposure to the high-born Bentley Drummle, who nevertheless "was idle, proud, niggardly, reserved, and suspicious," Pip learns that one's social status has nothing to do with the inner makings of a person.
On the other hand, the socially-awkward, illiterate Joe is always gentle in his heart, loving and loyal to a fault. For instance, when the intuitive Joe visits Pip in London, he apologizes to Pip for embarrassing him,
"If there's been any fault at all today, it's mine. You and me is not two figures to be together in London, nor yet anywheres else but what is private...and understood among friends."
Later, Pip realizes the value of this friendship and returns as the prodigal son, begging forgiveness, "receive my humble thanks for alll you have done for me, all I have so ill repaid." Lovingly and graciously as the best gentleman would, Joe replies "God knows as I forgive you, if I have anythink to forgive!"
The old convict Magwitch, too, possesses this gentle heart, as well. Ridden with guilt at his earlier intentions to "desert him," Pip tends to the injured convict on his death bed and tells him of Estella's existence; Magwitch kisses Pip hand and passes away.
Love and loyalty supercede all other values
For all his pursuance of Estella's attentions, she continuously treats him cruelly, explaining that she has no heart and is incapable of loving. Likewise, the superficial and self-serving Pumblechook, who flatters Pip only after he receives money and then takes credit for having been the "Mentor of our young Telemachus" and moved Pip up in social status, displays no redeeming qualities.
But, the noble Herbert Pocket and the humble John Wemmick prove the value of friendship to Pip as Herbert helps him try to get Magwitch out of London and Wemmick provides Pip fatherly love and advice. Of course, Biddy and Joe are loyal to Pip despite his rejection of them. In the end, it is Joe who tends Pip in his sickness after his rescue of Miss Havisham and both he and Biddy who welcome home Pip as though he has never neglected them.
Indeed, the evidence of love, friendship, and loyalty come not from those who appear lofty and grand and beautiful, but, rather, from the plain, simple, and decent people in Pip's life.