Seeing as you are still in levelling phase I advise to meld some Vit in jewelry, then Crit > Det.

Upon reaching level 70 and having your end game gear, I'll go Crit > Det > SpS.

I think that White Mage has the tools to never run out of MP so I think the whole "SpS will make you run out of MP faster" is moot AND no need for piety ^^

My two cents ...