I know it helps in mana regeneration, but I've tried to get gear with #1 INT #2 + spell damage and #3 stamina.  Am I making a mistake in not worrying about spirit?   

tier gear will give u spirit. dont go for gear specifically to get spirit at the expense of other stats tho

keep in mind, spirit is useless for a mage unless u get arcane meditation in the arcane tree (or spend 5 secs + doing nothing)

Forget spirit. That is what conjure food and conjure water is for.

spirit is good cos i hate eating and drinking. it stops gameplay. but if you take up spirit you sacrifice other stats which are more important. guy above says it like it is. conjure is cheap so use it. its a pain in the arse but we have good dps

You can also put on your Mage Armour too.
Anyway, spirit is only useful in raids.

I stuck on my mage armour, popped my evocation, mana pot, 3x mana emerald and I still ran out of mana on a boss.
It's an intellect problem and not a spirit problem right? :)

spirit isnt that great, its better to get gear that regenerates mana regen per 5 secs , because it applies while casting.

sorry about the redundant wording above, i wasn't thinking.

I am not sure that mages were meant to regenerate a lot of mana on there own they do have three options that has nothing to do with spirit.

Mana Potions obviously, I have had friends who specifically trained in alchemy to get a alchemist stone to augment their mana potion regeneration.

Evocation, which due to its timer will probably only be used once during a raid. Evocation was changed so that it returns based on your mana, not spirit.

Mana gems: the cool down on these are 2 minutes but the normal raid boss fight is around 10, some mages conjure lower level gems to combat this, I prefer to keep 1670 mana saved when low doing wand damage if I have to, to conjure another one and immediately use it when the cool down to use it is ready, I don't like doing it any earlier because I might need an emergency shield, counter spell, or sheep the mana is there and when you conjure and pop it at the same time you will have a return of 670-790 mana while a un summoned mana ruby would return 1073-1127 mana, however by the eight minute of the boss fight the second use of that emerald un summoned will return 2340-2460, which is a much better return then trying to use a mana citrine after a ruby ( 829-871 Mana return ). the difference is with emeralds 3010-3250 versus ruby & citrine 1902-1998.

Potions and gems should be timed for used as soon as your mana level drops below a level that their maximum return is not exceeded, any sooner and your wasting mana, any later and your going to waste your cool down timer on gem and potion use.

Even with these tricks I think Blizzard intended for us to drink & eat while soloing or else be paired with a shadow priest or shaman to get mana back.