there are only 7 orichalcum + in the game. you need an energy crystal as well to halve the amount needed. you need to clear atlantica, clear 100 acre wood, win the goddess of fates cup, it's a treasure chest in the brink of despair(in the world that never was), a treasure chest in Twilight Town(Sunset Terrace, on a rooftop), a treasure in Space Paranoids(Central Computer), and you need to collect every type of shard, stone, gem, and crystal. As for Serenity Crystals, just equip the Lucky Lucky ability and fight monsters. A lot of enemies drop it, like Shaman in the Pride Lands, or even Nobodies in the World that Never Was.
sig credit goes to Craizen
Resurrection in process:
Final Fantasy Eternal