Moira is more of an inspiration than a proper guide, since the narrator doesn't follow her example. Although we never find out the end of Moira's story, she seems like a beacon of light and hope for the narrator throughout most of the novel. She is the one who stands up to the Aunts at the Center, who resists the stupidity of the new rules, and who demands her old life back. Even before the war she had fought for feminism and equality, already working as a member of that shadowy resistance. The narrator and the other women at the Center need her as a model and vision of hope.
Aunt Lydia is a perverse, evil guide to the world of Gilead – a guide the narrator is forced to follow, at least on the outside. It's her voice the narrator hears over and over in her head, serving up platitudes about Gilead and the role of Handmaids. Throughout the book Aunt Lydia does traditional guide-like things, like providing advice and serving as a pseudo-mentor, but this "advice" is just commandments dressed up with Biblical references.