I don't particularly care for the relics stats...but IMO you should get the zenith, at least. Mostly because the armor can simply be farmed while you're building up myth by doing coil.
Get the Zenith and above i70 through some Crystal tower and by being prudent in selection of soldier/myth gear. Then coil away. You pretty much need coil gear for the accuracy. Though, I suppose you can get through Ifrit EX with just myth gear to get the Haken for accuracy.