So this specific guide/build all starts to come together Mid-Late game. Of course every match is situational so everything past TF is situational, but preferred is most match ups.
Runes> Electrocute > scales with AD burst quite well. Since were mostly stacking Damage with these items your 3rd attack will have High damage. Specially if AA>Q>AA combo as you can get 3 attacks off in less then a seconds if done right. And that 2nd AA will have lethality, TF Proc, and Electrocute.