I'm level 12 and just specced into Rift mage. What is a good build for me to have at this level? Right now my abilities are:
Stonefist, Veilstrike, Pull of the Abyss+, Immolate, Chain Lightning+, Energy Barrage, Barrier, Mark of the Rift.
I have every talent in the Rift tree except for the Firestorm unlocked. Is this wise, or should respec and limit the # of points in this tree? I also want to get a bunch of other talents from the other trees I just don't have the points 
IMO, there are two "key" passive abilities for an ideal Rift Mage build.
Restorative Veil, from the Rift Mage Tree <- your most important passive, the key to infinite mana. to use it properly, you must weaken enemies.
Clean Burn, from the Fire Tree <- 1 second cooldown reduction on all spells gets nice real fast, especially when you have infinite mana
So, the key is to Weaken enemies using your Rift Mage actives, then unload on them with fast-cast (aoe!) damage (to recharge mana), then weaken them again, then more damage...
14 talent points:
Veilstrike, Restorative Veil, Smothering Veil, Pull of the Abyss**, Stonefist**, (7)
Immolate**, Flashpoint, Clean Burn (4)
Chain Lightning** (2)
Barrier (1)
15th Talent point: Respec to Twisting/Encircling Veil instead of Smothering
16th Talent point: Upgrade Veilstrike
17th Talent point: Get Smothering Veil if FF is off, imo ignore if on
17+: Your call. I'd build towards a fully upgraded Fire Mine because it combines so well with PutA.
I built Solas this way and he's been pretty monstrous. I can only imagine how nasty he'll be with Fire Mine - I've currently got Fire Mine on my Mage Inquisitor and it's pretty nasty just following up AI-controlled Solas's PutA's (protip: if you're not gonna micro him, set Veilstrike/PutA to preferred tactics). Protip 2: If playing with FF off, enjoy the synergy with a 2-handed warrior. It gets silly FAST.