Your attributes, perhaps, should be Agility, Willpower, Presence. Use Spiced Wine for boon to maximize Toughness.
However, I would say that the reliability of the mechanism is equal to the reliability of the most fragile part of it (i.e. your companions, which are often not tenacious enough for my taste), so you can not worry about Toughness, but instead invest all your points in Willpower, Cunning, Presence. Apple Cider is used as boon to maximize Agility.
Use the
Metal Wand from the wandering caravan as a weapon. Why? Weapon with storm damage, ranged. Off-Hand?
Mage Wand from Ivris (because among the catalysts available at that time, this has the best stats overall). In terms of magical stats, this combination is inferior to the
Spiraled Staff only in
crit terms of Spellpower (5 less). Later it will be possible to replace the
Mage Wand with
Blank Scroll (+5 spellpower, -5 crit)/
Bull Totem (+10 spellpower -5 crit) or
Shield Orb (a shield that increases magical abilities), although I somewhat dislike the penalty to crit and the lack of bonus to accuracy. You can also try using
Harp of Waves, there is no spell penetrative, but it increases Leadership and opens up the possibility of using a new Power (
Aria of Waves, it seems that this Power had some kind of low damage bug in the past, but I think it was fixed a long time ago).
For armor, I would use
Leather Jerkin and quickly switch to
Lamellar Armour (for my taste, physical damage is the most dangerous type of damage in the game, so I would give priority to protection against it). If your tank/damage dealer is good enough to draw attention to them (I mean high Threat Level, which after version 0.5.0 finally works properly) and you are not afraid of enemy damage, then you can also use
Tiran Nun's Habit /
Tiran Vestments. Also in the case of using fire or blight spells,
Regal Kimono is a possible option (you get this from Tetsuya, it seems this item just appears in your inventory or I was traditionally inattentive and did not notice the moment of gifting). Why? Well, this item seems to increase the damage of all fire and blight attacks by 20%.
On the shoulders?
Leather Spaulders as the only hon-heavy item with the physical resistance (save rolls against some atacks). After Winter City can be replaced with
Seaweave Shaman's Cape for immunity to Sundered. I would not rule out other options, but I would call the items known to me more situational. I'm talking, of course, this is only about the items that I knew at the time of the update, do not forget to check the wiki in case other interesting options appear.
As a belt,
Champion's Belt and
Senninbari are arguably the best options. People who focus on maximum Spellpower can use the
Reagent Pouch, but personally I prefer not to forget the protection that other belts give me.
Amulet of Transference/
Amulet of Union is very good, but I would not rely too much on an item that will one day be taken from you. So
Serpent Locket or
Fluffy Scarf are probably the best options.
The rings, of course, are the
Wizard Ring, after receiving the
Mare's Ring you replace one of them. I would consider wearing two
Lucky Strike, but I'm not sure how useful it will be, a similar situation with
Ring of Fortune....
The best At-Will Power, I think, will be
Equilibrium (taught by Zo). Because I hate being knocked prone and missing the turn. Disarm Immunity are not as useful for a mage as for a warrior or a thief, but it's nice to have it too.
Recharge Powers. The
Grease+
Fireball combo is still effective, but when fighting opponents with resistance to fire, I prefer to use
Crackle Powder+
Arc Cannon. By the way,
Crackle Powder is the main reason to use
Metal Wand, despite the fact that the
Control Rod is better.
As an Encounter Power,
Vitality Reap,
Summon Wolf Spirit and
Summon Phyria looks best, choose one of these three abilities depending on what kind of enemy you expect to meet.
Ultimate... I find the
Banishment effect somewhat weak, but logically it's a useful ability and in a fight with a strong opponent, the opportunity to buying yourself some time can be invaluable. Also, this ability can provide instant victory in certain battles, but this only affects Ethereals and Constructs.
But you better not use it against Synneva and Queen Atheldred, it blocks the best possible solution to the event.
Companions.
Queenly Raiment Ryn as a healer. Cait in her witch attire may seem preferable, but Queen Etheryn has one very important trump card... the
Blessing spell, which increases the damage of your next attack by roughly 50%.
Who is the third?
Hexblade Leathers Cait as a single target damage dealer.
Winter Knight Brint doesn't fit the group as well as Cait for my taste, but not bad either.
Kami-no-Michi Kiyoko has not been tested as a Black Mage follower, but her abilities look mind-blowing. Also in some version she got a new set (
Kanso) that makes her kind of a mix of tank and healer, a very good set, these two rounds of near invulnerability will be very useful in fights with something like the Faceless Blade.
Agnimitra? Her Encounter and Ultimate abilities look good, but in my opinion she is not the best addition to the Black Mage group. Also, her buff is gaining strength too slowly, I would say that by the fifth round, most of the battles will be over.
UPDATE. WOW! It seems that my old advices is still useful to someone, despite being outdated and having errors. In this case, I corrected the errors I noticed.
Also added a little new, more relevant in current versions, but does not make sense at the time of version 0.4.28, when my comment was posted.