Shield 1 always 1st. I can't recount just how many times it saved my arse, or my teammates arse (whether they have been chasing a kill, not known about high towers, about to be nuked etc)
If i can get some early gold, a cheap kill etc normally ill get another mana helm (or perhaps tell teammates i have cash for currency) and spec penitence early.
If the opposing team really isn't using interrupts much, then 1 level in shield is fine to do all the tricky stuff, as long as you are aware of what you need to do. i.e. shield and quickly scroll for tp etc or shield and spam potions.
If the enemy pushes early with creeps, or goes hc creeps, i try to spec more into divine justice. I normally get DJ pretty early, because of the mana regen, from last hitting all the creeps. Or even the monks, or those pesky minions.
Normally though, i make up my mind on how to play depending on the first 5 or so levels, then spec from there. You can normally tell if people are cautious, holding back, overeager, minion using, spammers etc
Normally i start off the 1st four levels the same though, and then specialise from there.
For favour it varies depending on the team too. Monks + Botf is always a good move though, Cloak of night is always enjoyable on crucible and exile. The minion regen/damage work well too if you are up against some non-aoe DGs.
Normal Kitch build for a cataract 3v3.
1. Shield 1
Always shield first.
2. Soul ward 1.
3. Raise dead ward 1
4. Divine justice 1
Soul ward and raise dead with spirits makes oak do about 220-240ish demage depending on how many spirits you have. This is very good for finishing off creeps, which complements divine justice early really well. Also, allows for attack of towers with raised DPS.
From here on in it depends on how the game goes. Early kill + gold, mostly penitence. If not, the surge. Lets go with an even game, and surge. Because of the aoe, you can surge an area to tag the creeps, and run away with the +speed when on low health.
5. Surge of faith 1.
6. Pen 1. (most people have decent nukes/potions worth interupting by now)
Decide now how the games going. Most people are getting mana/spamming things by now. Few directions. Spirits, Assasin, or in need of un-interuptable shield. Normally its a choice between some more damage if we are winning, or an un-interuptable shield combined with teleports if I'm getting ganked/losing. Lets say its still even.
7. Pen 2.
8. Pen 3.
depends here if they are using interupts much, and are consistently ganking. If so, shield time. If not, then spirits.
9 . shield 2.
10. Surge 2. Kills most of a creep wave just through activation.
11. Pen 4./Raise Dead 2
12. Shield 3
Depends now on how many creeps they have. If a lot, and you are being pushed back, then DJ. If equalish, the you want for the harrasment ability and the extra weapon damage.
13. Raise dead 2.
14. raise dead 3
15. Surge 3.
16. Raise dead 4.
17. Divine justice 3
18-20 whatever really, probably won't even get there.
Things to remember.
Level 4 raise dead ward gives a 400 armour bonus to unit in area. Same level as level 4 citadel creep armory?
Shield all levels debuffs. Shield 3 onwards blocks interupts.
Soul power is just +20 bonus damage each level.
Penitence before surge increases surge damage on a target.
Spirits are easily acquired and will rape face if specced properly. I selects spirits independently for S.A.S style raids on towers forts, demigods etc.
Your teamamte will always at some point require a shield.
Surge damages buildings.
Lure enemy into range of creeps. Fight battle amongst creeps and surge. ??? Best the rival demigod.