I'm not sure of the best way to handle that, although playing the Meditation Amulet first turn will probably work better. I don't think Graveyard has a minimum amount of mana needed to deploy a creature, in which case you come out slightly ahead playing the Meditation Amulet before the Harmonize.
The issue is that there aren't any really good defensive Nonliving dark creatures that are cheap enough to get out turn 2 with that type of opening. One of the reasons I like Lair -> Meditation Amulet turn 1 is Timber Wolf is such a nice creature for defense if that becomes necessary. I would probably play a turn 2 Deathfang, and hope to hinder my opponent with the Deathfang in order to slow them down. Then if they're rushing me, I would meditate and play Dragonscale Hauberk, if not, meditate and play Harmonize, Death Ring, or a Mana Crystal. You could also use Skeletal Sentry. A Skeletal Sentry isn't as good a guard as Timber Wolf, but you could start healing them efficiently later if they survive, and if they die, it feeds your Graveyard.
As for Libro, I wouldn't cast Harmonize on it, as that leaves you vulnerable to an efficient Dissolve/Explode. It becomes efficient enough with Death Ring anyway.