“First,” said Mr. Jaggers, “you should have some new clothes to come in, and they should not be working clothes. Say this day week. You’ll want some money. Shall I leave you twenty guineas?””
In telling Pip to get rid of the working clothes look, Jaggers indirectly insults Joe and indicates that Pip won’t be associating with the working classes anymore. Money divides people: this seems to be first time that Pip and Joe won’t look like each other.