A figurative gift is something that is not literal. For example, Atticus tells Arthur “Boo” Radley thank you for the figurative gift of his children.
Near the end of the story, Scout and Jem Finch are attacked by Bob Ewell on Halloween. Ewell is angry at Atticus because he feels he made a fool of him during Mayella’s trial. Boo Radley steps in and protects the children, killing Ewell. Atticus is aware that if Boo had not stepped in, the children might have succumbed to worse injuries than Jem’s broken arm.
When [Atticus] got up and walked across the porch into the shadows, his youthful step had returned. Before he went inside the house, he stopped in front of Boo Radley. "Thank you for my children, Arthur," he said. (ch 30)
When Atticus thanks Boo for his children, he is actually saying quite a lot. He is grateful to Boo for saving his children’s lives. He is grateful to Boo also for looking out for them. Boo put the blanket on Scout’s shoulders during the fire, and mended Jem’s pants. Boo was, overall, a good friend. Friendship is the best gift of all.