Ok, I think this may do the trick :

str 54 or around this number depend the armor and weapon. minimum should be 54
con 20
dex 20 (+1%critik)
int max possible

for the first levels, i will raise asap con and dex then each next level +4int with +1 str
what do you with of this?

thanks

I leveled as a support (focused on buffs and heals mostly, with keeping plume quill maxed to solo); don't do it unless you have a very good guild with a lot of active people, or even better, a group of friends to level with.
Like trikilon said, keep dex at 5. If you really want crit, you can buy rings with it later on. Only raise your strength as far as your equipment requires you to, and toss the rest in int, with the occasional point in con if your gear's a bit so-so (doesn't come into play until lvl 20-30 though, so no need to worry about it yet).
The problem is that grouping for regular quests isn't all that rewarding for most classes for a large part of the game, meaning that leveling a support priest is going to make you very sad when plume quill isn't all that hot anymore D:
I'm 49 atm, with 2/4 buffs maxed, most of my heals at a pretty high level, and plume quill maxed. And I got enormous trouble killing things my level because my damage just isn't coming out fast enough anymore (having to rest every other mob isn't all that uncommon for me).
While I have been told that these levels suck because the mobs do physical damage, that doesn't really do much to encourage leveling when I lose more xp than I gain. So I'm desperately trying to catch up with some damage spells now, hoping for the best.

So, this semi-rant aside, here's some serious advice as far as skills go.
Keep whisht heart (the heal that heals over time) maxed.
Keep resurrection maxed when you get it.
Pick either pure heart or sapience pour maxed, and level the other one when you have the spare sp.

Everything else in the healing tree line can be kept at 1 until lvl 60+ (not my personal experience, but it's commonly agreed upon)

At lvl 29, you will have a total of 4 different buffs to level. You can't do this because it just costs too much sp. If I would level a new priest, I'd focus on 1 buff at a time, raising the others when I got a particularly large amount of spare sp (after completing cultivation quests). I would prioritize solid shell over spirit gather, because robes give plenty magic defense, but very poor physical defense, and solid shell will enhance the effect of physical defense stones quite nicely. I just don't know which of the other two buffs would benefit you most; increased magic attack is great, but when you get it, the effect on plume quill's damage isn't that noticeable. Increased health and mana regen is more versatile because everyone benefits from it, and it -can- make killing a bit easier on the potion consumption. It's a personal preference, really.
On the other hand, you can of course try to keep your buffs on even levels; this is pretty hard to do because of the gap in levels between the first buff you learn and the last.

As a support, you have little use for the hex line of spells, so skip them completely until you want to go pvp or so <.<

Plume barrier may be nice in a pinch, but I just never had the sp for it, always something more useful to level x_x
Even if I'd level a damage dealing priest, I'd leave the spells that affect more than 1 enemy for later on; I prefer my fights 1 on 1, so I'm hopping over Feather Razors regardless.

Now we get to the big kicker; the metal damage spells. There's no way around it, you simply need something other than PQ at higher levels. What that something might be, I don't know yet, which is why I'm testing and comparing damage of low spell levels and asking other priests.
Great Cyclone slows stuff down, which is nice if you're not lagging to bits and can kite things, else it's at about the same level of damage as PQ.
I'm thinking of getting thunder sphere for some continuous damage, and thunder wield because it seems to pick up at lvl 1 where PQ leaves off at lvl 10; coincidentally, you can max out PQ at lvl 45 and start leveling thunder wield at lvl 44
As I said before, I'm hopping over all AoE spells, as I can't handle more than 1 mob at a time, and in a group, my job won't be doing damage.

In short:

Level as soon as a new skill level is available:
- whisht heart
- resurrection
- pure heart OR sapience pour
- plume quill
- the buff you decided to focus on (if you take this route with buff leveling)

Level after your "main" skills, if you have spare leftover sp:
- level 1 in skills you intend to level later on; skills that have some use now (best example is purify; it does the job at lvl 1 at the time you get it)
- buffs/heals you're not focusing on right now, but will focus on soon
- damage skills you'll need after you maxed PQ; most of them are cheap for the first few levels, so you can see what works for you.

Stuff you don't have to level:
- The hex line of spells
- AoE damage spells (unless you need to buy lvl 1 to unlock a spell further down the line)
- flight mastery

Your con needs to be way higher than 50 at a 'final build'. If you want to survive any higher lvl boss aoe attacks (such as in the Holy Hall), you need a base of at least 2.8k hp (that's without max hp buff from WB).

I'm not really sure about that. I don't pvp much and don't think crit will really play that much of a role in winning if your con is very low.

In response to Inori:
The curses are very useful at high lvls, after you're done lvling other things, go back and learn them when you have nothing else to spend SP on. AOE spell like hurricane doesn't work at low lvl, but higher it will. Galactic Storm is a good thing to lvl for war or pvp. you can kill a few people in one hit.

Ok.. Well sometimes agi is good. Your not ALWAYS going to be fighting a magical mob, theres physical quest mobs. Con is a no no. You should put hp stones on armor and use hp helm. Wearing stats for light armor I think is best... I saw an EP in holy hall with 112 agi who was attacked by Asura close range and Asura missed! Her agi saved her life. Same in zhen leveling. You are attacked by physical mobs so your being able to wear light armor and having dodge helps a lot. My current build(with extras on armor) is:
9 con
73 str
242 int
67 agi

I'm level 70 right now and 71 will be the last level I add agi for quiet a while. I wear armor with +hp stones and I have a second set of light armor for things like zhen and HH.
Also people think not putting full int hurts you in your magic attack area but mine is currently 5k magic attack. I crit at least once on every mob I fight and when it comes to physical or pvp I have high enough dodge that people and mobs miss me.

I hope that helps.

thanks all for these opinion for EP. 306 for Holy Weapon.... didnt know lol, my current stat (lvl 50) is
unequip/ equip
38 con 52
35 str 39
38 agi 40
154 int 157
At lvl 50 with my stuff lvl 43

I have all attack lvl 1 like thunder wield etc... and cyclone 8 plum quill 6
Rez 7, Buff PDEF 10, Buff MDEF 10, Buff regen HP/MP 7, Buff Mattak 5, Whilst Heart 9, sapience pour 6
party PDef buff 1, party heal 1, rejuv 1, dispell 1
no debuff.

34kSP left.

nevertheless, i was going to raise my int as high as possible. my agi/str/con are final I think I dont think I will change. All armor wil be equiped with soulstone HP.


EDIT: i raised my skills like plum quill and cyclone because in pve its really usefull. Those who want to become full support shouldn't raise the right side of skill tree, I mean thunder wield etc... just plum quill and cyclone. in fact, in pve i do not use my right side skills, it consumme too much mana. I think if i was to rebuild a priest I will go that way raising skill :
priority of lvling, like Inori said :
Whilst heart spell
all buff, regen HP/mana is a priority
cyclone
plum quill
resurection
party heal

then at higher lvl raise thunder wield, first AOE (thunder of heaven i think its the name) and galactic storm
very important i think are metal expertise but its quite expensive. should only be pump at lvl >60
also learn the doom skills that are only learning no need to lvlup. they are quite useful for AoE party.

with low health, you won't be able to pvp or GVG for long, its like full dex archer PK... By the way, i raised my dex but as a support dex should stay at 5 or less if you can restat. but further as you lvl up, you may want to start pvp then i should say to sacrifice some hp for 40dex, try to match equiment you have. for example I have 38dex right now but 40 with equipement. when you think its necessary you should restat some points of dex which are not necessary, like having 43dex, the point you have this way are very significant because it will add you a lot of HP.
My priest yesterday at lvl 52 with lvl1 thunder wield and +2 molder 43 quoit, did on wood with furyburst 2critical in a row at 9700dmg on elite mob of FB39... i was quite happy. it seems that with 4% critical priest often do critical, i dont really know. if someone knows about "random critical" mechanism plz advise me.

thx all for your help, cya ingame
on Delphi : Here EP52 spé Heal