Hello mates this is my first guide that's why it's for my real main: Diana. I play her with an attack speed build to be more powerful in late than the classic build.
I hope it will help you to carry with Diana!

Pros:
- Incredible burst
- Very low cd
- Easy and funny to play
- High Mobility
- Great Combos

Cons:
- Vulnerable to ganks
- Weak against offtanks
- No escape when engaged
- Weak before lvl 6
- It's hard to kill when Q don't hit

- Mark of Attack Speed x9 to help your passive to proc.
- Seal Of Armor x9 because Diana has to be tanky.
- Glyph of Magic Resist x9 for the same reason.
- Quint of Ability Power x3 to improve Diana's awesome burst.

For the masteries, Deathfire Touch isn't bad but I prefer 12-18-0 with Thunderlord.

Ferocity: 12
Fury
Double Edged Sword
Vampirism
Bounty Hunter

Cunning: 18
Savagery
Assassin
Merciless
Dangerous Game
Precision
Thundrlord's Decree

Resolve: 0

Start:Standard start with AP and Mana Regen.

First Back: At first back take Stinger if you can. Otherwise, go Fiendish Codex.

Rush: Nashor's Tooth give you awesome burst and Attack Speed. If you need burst, you can take Sorcerer's Shoes.

Sustain: Gunblade gives good damages and the survivability you need.

Core Items: Take Trinity first to CDR, Attack Speed and damages, then take Guinsoo.

Last Item: Take Banshee against Hard CC or Guardian Angel for tankyness. For full damage or against heavy AP go Wit's End.