I have a Human Knight Enchanter that I took my time leveling with, that's how I found the level cap of 27.
That said, he has 31 ability points, (+1 for race, +3 for Inquisitor Amulets)
Basically, I have all the passives from all the ability trees, except for the bottom on the Winter tree, since I don't need it.
Even if you don't have a high level mage, the only Passive that is "necessary" for this is Flashpoint, which you only need 2 points in the Inferno tree to get to. The Knight Enchanter passives are important to have and go extremely well with this, but even if not, it is still an effective staff.
The staff I use is the First Enchanter staff, a Tier 3 schematic. Not only is it my favorite staff via appearance, but it's crafting slots fit what I'm looking for in a weapon.
Damage: 22 Metal
Offense: 6 Cloth
Offense: 6 Leather
Utility: 6 Leather
Masterwork: Yes
Rune: Superb Cleansing Rune (honestly because I think it looks the best) or Superb Spirit Rune.
For Damage I use Dragon Bone, which makes it a fire staff
For Offense (cloth) I use either Plush Faustian Velvet or Kings Willow Weave, whichever I have more of, for attack increase
For Offense (leather) I use Dragon Webbing for armor penetration
For Utility I use whatever grants the most Cunning, for critical chance. Usually Lurker Scales or Imbued Tusket Hide.
The Masterwork is always Fade Touched Silverite, for the guard gain per hit.
The Dragon Bone and Webbing is simple enough to get, just find dragons and slay them.
I tend to find more Velvet than Weave simple due to there being more Venatori (velvet) than Darkspawn (weave)
Lurker Scales are easy to get once you can access the Hissing Wastes, since they respawn frequently, but once I get to the Frostback Basin the Imbued Tusket Hide wins out.
The Fade Touched Silverite isn't too hard to find in the Emprise du Lion, since Silverite is EVERYWHERE, so as long as you are diligent with collecting resources, you're bound to stumble upon some soon enough.
As for upgrades, that's where I get my boost to Magic/Willpower/Constitution.
The Blunt Staff Edge gives you a total of 9 Cloth Utility slots, so I fill it with as much Magic boosting cloth, either Dales Loden Wool or Royale Sea Silk (+1.75 Magic), but as soon as Silken Nether Cloth (+2 Magic) is available, I use that.
As for staff Grips, I like to use Split Staff Grip, it looks good with the Blunt Staff Edge and the look of the First Enchanter staff, while having a Utility slot for Cloth and an Attack slot for Leather, to further boost armor penetration.
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As a Knight Enchanter, my damage output isn't as great as Solas or Dorian, so the armor penetration is helpful in boosting damage.
The Cunning boost from the leather Utility increases my Critical Chance, improving my chances of activating Flashpoint from the Inferno Tree, which improves the number of spells I can cast, which increases both my Guard and my Barrier due to F.T.Silverite and KE passives.
Rejuvenating Barrier and Combat Clarity increase my mana regeneration by a total of 85% when I have barrier active and when enemies are close; and the Strength of Spirits and Knight Protector together give me a stronger Barrier that lasts longer, and Guardian Spirits give me an emergency barrier on the rare occurrence of my health taking damage.
Add in Veiled Riposte (damage returned to attackers) and Fade Shield (gain barrier from damage dealt), and you get someone who only gets tougher and stronger the more he's surrounded, and deals more damage and attacks the tougher he gets.
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All combined, I have a stately-looking gold-colored fire staff, blueish-white corona with upwards of 50% armor penetration, carries a hefty Magic bonus, and grants Guard with every attack I make.
Oh, and I call it "Maker's Will" (my Inquisitor is faithful)
Anyway, I like it because it looks good, fits the roleplaying aspect, AND has great game mechanic synergy. I can solo with this no problem.