Head over to the Relic shop and into the trees nearby. You’ll find some guy in there who apparently snuck a piece of Magicite out from the Research Facility. He’s offering you it for a mere 3,000 Gil. I highly suggest taking it right now. (You can get it later, in the World of Ruin, for a mere(r) ten Gil. But it’s useless by then.)
Seraph is quite definitely the best Esper you can have right now. It can restore all allies’ HP and teach Cure, Regen, Cura, Raise, and Esuna. Our next stop is Jidoor. It is on the southern tip of the northern continent, south of Zozo.