Hey guys, my name is dunkman20. I'm currently a gold euw player and i'm an adc main. Xayah is the champ that i play the most and i want to share u my own guide on this champ.
Let's started !

New Runes system didn't up or nerf Xayah. For me, she still have the same impact on the game.
For the first branch, we will go on Precision and Press the Attack. For the other runes u can take what u prefer (according to u'r play style).

For the items, i can just add some explanations. Critical damages are very important on Xayah, this is why u have to rush Statikk Shiv and Infinity Edge or Essence Reaver. As a lot of other ADC, u will need some life steal --> Bloodthirster. For the other items, all is depending of the situation.

Pros

Strong at all stages of the game (early, mid and late).
Can cc the whole ennemy team with Bladecaller
The only Adc who can be untouchable for a few seconds.

Cons

Almost no cons.

When u are fighting with u'r team, try to stay behind u'r mates. U'r objective is to put a maximum of daggers behind ennemy teams. When u feel that it's the right moment, u can try to cc them with Bladecaller and os some of them.

The farming is quite simple with Xayah. Double Daggers and Bladecaller are very good spells to farm. Moreover, u'r passiv Clean Cuts can help u t take some creeps who are far from u on laning phase.