spirit or stam for a low lvl priest?Follow

Don't entirely neglect Sta but Spi is more useful for a levelling priest as Spirit Tap (which I'll assume you've got) gives better returns at lower levels.

As stated, depends on Spirit Tap, but I would rank Spirit (if you have Spirit Tap) first, followed by Intelligence to increase your mana pool, and then Stamina last.

Unless you play in lots of BG's, you should not be too worried about stamina. Up until level 40 if you are shadow you will still have access to all your heal spells while fighting, so you can throw a renew or heal as needed while casting damage dealing spells. Spirit Tap allows for faster mana regen and can create the ability to go almost non stop without having to rest for mana. Intelligence gives a greater mana pool which allows for that extra spell or two to be cast between rests also.

So in my opinion, forget about Stamina until you hit the outlands unless you plan on playing lots of BG's. Even then, not really needed until later levels.