Luke wants to recreate the Jedi Knights, a mission he feels particularly committed to for his niece and nephew's sakes. After various false leads (and a whole lot of scoundrel-related trouble--oh Han and Lando!), he thinks he might finally be able to start another Jedi Academy.(Although after seeing the prequel movies, Luke's dream seems completely disconnected from reality. Jedi need training, yes. But the ancient methods were clearly completely idiotic. Raising the Jedi to have no friends or loved ones from the age of babies is just asking for trouble.)