What does Pip learn about being a gentleman?

When Pip first learns he is being financed to become a gentleman, he moves to London, finds fine lodgings, and buys expensive clothing. As his own status elevates, he becomes ashamed of Joe, a humble blacksmith. He feels superior to him. He even tries to avoid seeing him, despite all the kindness and compassion Joe showed to him when he was a child.
As time goes on, however, and Pip learns that Magwitch, the convict, is his secret benefactor, he begins to be humbled. When Pip learns to love and appreciate Magwitch despite his background, he begins to change. When Joe pays his debts and treats him with forgiveness despite all his former snobbery, Pip realizes that a true gentleman isn't defined by his wealth or outward appearance. He grows to realize that what counts is a person's character or soul: what they are on the inside. Joe may be a humble blacksmith, but his generosity, gentleness, and compassion make him a true gentleman. Pip thought he was a gentleman because of his fine clothes and companions, but realizes that was all external: he was nothing but a snob.
The humbled Pip goes to see Joe and his new wife Biddy, who is as good as Joe is. Pip promises to pay back all he owes them. But he wants their good opinion, because he now knows their worth:

And now, though I know you have already done it in your own kind hearts, pray tell me, both, that you forgive me! Pray let me hear you say the words, that I may carry the sound of them away with me, and then I shall be able to believe that you can trust me, and think better of me, in the time to come!
O dear old Pip, old chap,” said Joe. “God knows as I forgive you, if I have any thing to forgive!