Hello!
Kiari is actually my 2nd newest Master next to Yan Lo but in the few games I've had with her she has lived up to her reputation as being both a tricky one to use and also to play against.
Like Alf mentioned she favours spirits but
tbh once you get to grips with her synergies and rules that affect spirits, you don't tend to miss the regular resser Minions. (Not even Canines or Flesh Constructs!

). That said, if you take a non-spirit beatstick (such as Izamu or Dead Rider) and use Lost Love to turn them into a spirit (which remains for the game!) Then they become quite unstopable!
Alf mentioned the Seishin and these little guys are basically the key to the whole crew. For nearly all Kirais spells/actions you need to sacrifice a friendly spirit. Obviously you dont want to be sacrificing anything decent so you'll want your Seishin close by. This isn't hard as whenever a Seishin is not in base contact with Kirai you can move them there at the end of ANY models activation. Which is really useful if you have someone trying to Lure them away!

Your opponent will try this as if you have a Seishin by Kirai she can nominate it to take the effect of an attack! Which is nice!
I have lots more to ramble on about but I'm at work at mo and i have to close down for the day! I'll try jump back on later this evening to add more!
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A little more on Seishin, theres a nice little trick to bring back one of your spirits that has been cut off from the rest of your crew. Kirais switch spirit ability has a decent range of 12" and while its primary use is probably to sent your beatstick into combat its useful to bring one back. Basically if one of your spirits is getting a bit mullered or has been badly postioned then use Kirai to switch said spirit with a Seishin (which is likely to be b2b with Kirai) this gets your more valueable spirit out of harms way and of course, when Kirai ends her activation the Seishin you switched will come running back!

Leaving your opponent sat in the middle of nowhere having to rethink their next move! Situational obviously but its worth noting!
As useful as they are dont always rush to hire the maximum of 5 cause anything other than a construct that dies with 8" of kirai will generate on.
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A couple more things to think about:
Lost Love is a must! As I mentioned you can use him to turn your beatstick into a spirit but if you dont do anything with him the entire game its still a must have. This is due to the rather useful rule allowing him to be sacrificed in the event of Kirais death. And not only that but when this happens Kirai regains 4 wounds and gains the spirit characteristic for the rest of the game! Nice!
In regards to the Ikiyro. Dont think of this guy as another minion but rather part of Kirai. Although it seems costly to suffer 4-5 wounds on Kirai to summon it in, you shouldnt be put off getting it out as often as poss. Think of it as more of Kirais melee attack. (Cause her own actually attack is almost useless but you dont need that anyway!

)
Dont worry too much about self inflicting wounds on Kirai to summon more minions! Datsue-ba, lost love and Kirai herself all have spells to heal spirits. Which if you send Kirai into the spirit world she can then be targetted. Note, you can always target yourself! Dont forget that every time the Ikiryo kills an enemy model Kirai makes a healing flip!
Need to go again! More ramblings coming soon!
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I think one of the reasons Kirai is considered a difficult master to, well, master, is the shear amount of spells/abilities her crew has. Just the starter box has Kirai, Datsue-ba and the Onyros who all have 2 full pages of spells/abilities which compared to most of the other ressers (bar the other masters of course) is rather a lot. A lot of the time its going to be fairly straight forward deciding what you want to do. But when faced with an opponent who can put on the pressure it can get quite probmatic for you and your crew to deal with several threats at once. Yes you have lots of spells/abilities but that means sometimes you'll need to be careful when and where to cheat fate. Which spell do you REALLY need right now? Whens the right time to summon a fresh spirit? Is Kirai going to miss those extra wounds? Can you heal her in time?
Ok, so most of that applys to most masters/crews and fairly circumstancuial. But with so many synergies between each of your minions its easy to spend all your control cards buffing your crew and then when your opponent suddenly strikes you'll be relying on fate itself!
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The spirit rule is rather nice with the whole halving of damage. However, while at first glance its uber hard, there are a few things to note. Most of your spirits dont have Hard to Wound (H2W). I find this a fantastic rule which more often than not is the difference between a straight or negative flip on the damage. Where a negative flip cant be cheated so you're more likely be taking weak/moderate damage, spirits who dont have H2W will be more often taking moderate/severe damage (your opponent will be more likely to cheat).
Eg. A model hits a canine remains with damage spread of 2/3/4. With his H2W helping, the model flips for weak damage causing 2 wounds.
Same model hits a spirit with same weapon. No H2W on spirit. Moderate damage causing 2 wounds.
So same damage. Worth noting, thd Spirit rule is not always uber!
And of cause! MAGIC DAMAGE = BIG OUCHY FOR SPIRITS!
With lack of H2W, slow to die and hard to kill on most spirits you will really be up against it when your opponent is armed and ready with lots of damage dealing spells or magic weapons. I have the Viktorias and most of their usual Merc minions have magic melee attacks. These are bad news for spirits.
I'm done for now! I think! Hopefully some of that was useful!