First off, The mythics. These mythics are interchangeable, but personally I choose prowlers because its busted and provides good mobility, also it works well with the inspiration tree, since Cosmic Insight is arguably the best choice from that row. My next pick would be Eclipse since it also works well with cosmic insight, and does better against targets with a lot of health. I would suggest taking it over prowlers into tankier team comps.


The standard Qiyana boots, but if you miss the out of combat MS from yomu (we will not be building it for now due to nerfs) you can grab Mobi boots or go domination secondary and get the Relentless Hunter rune.


Axiom arc is the new fresh assassin item that works amazing on Qiyana. Ability haste is amazing and a powerful ult like yours having 25% of its cooldown removed per kill is insane.


After Axiom I recommend Serylda's, but truth be told after Axiom go whatever you feel you want. Need more protection? Edge of Night. Against Shielders or Shieldbow users? Serpents Fang. The list goes on, just pick up whatever works in your current game.

Now, First strike might not be the ABSOLUTE BEST rune page for Qiyana. But if you can get first strike, and hit your enemy with your combo, You can do some gnarly true damage as well as get snowballing with extra gold. It's also easy to proc in the laning phase with your long range double Q's (Either ice Q > W > earth Q or Grass Q into earth to avoid getting auto'd) Using your grass Q to go in during the later phases of the game is essential to getting in that first strike rune, you want to make it your absolute priority to not get hit before you go in. Avoiding skill shots from mages will probably be the hardest part, while point and click abilities and autos will be the easiest (Use Grass Q). Other than that the other runes are for a little bit of movement speed and mana, as well as item and summoner haste. For secondary runes you can take POM for mana and Coup for extra damage, or get in which ever two domination runes you like (Go for sudden impact with Relentless Hunter or Ravenous Hunter). With this build you shouldn't be needing Ultimate Hunter, but if you really insist go for it.

Not much else, this is more of an insight to a new Season 12 Qiyana build, not an actual guide on how to play Qiyana. Look elsewhere for that my friend...
(https://www.mobafire.com/league-of-legends/build/ultimate-qiyana-guide-mid-jg-top-challenger-590371)