Hi I'm Drusif,
This is my first attempt to make any kind of post or any kind of guide for anything ever so forgive me if it sucks ha but I guess really all id like to say is here is my build for Diana I absolutly love her and i play a lot of assassins so i kind of built her kinda a little more like a glass cannon with emphasis on ability power, then spell vamp and attack speed and it works beautiful for me and my playstyle it's not really a guide just more for fun if you enjoy and are good with diana and want to rack up kills.

Pros:
Massive damage
Huge early game snowball potential
Great mid game massacre
Late game with so high ap/as/sv youre unkillable damn near

CONS:
slightly more squishy
mana hungry
very costly gold wise
very quickly focused
Very susceptible to CC