Hello and welcome to my guide for proper building attack damage Katarina.
In this guide I will explain you how AD works on Katarina and explain items, runes and mastery page that I'm using while playing with her.

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Enjoy reading, feel free to vote and comment.

Katarina has one of the best basic attack animations in the game, so using her basic attack to deal tons of damage is not a bad idea. She also has Shunpo which we won't use to deal damage with since it's not scaling with AD, we will use it to jump on the enemy carry and beat the **** out of him using both abilities and basic attacks! So when your abilities are on cooldown don't be scared to fight with your basic attacks.
Katarina's Bouncing Blades and Death Lotus are scaling great with AD so this makes this style of playing with her actually viable.
Bouncing Blades - +0.8 of bonus AD.
Death Lotus - +0.5 of bonus AD.

I don't say that it's better than buying AP, I even think that AP Katarina is better.
So if you want to hear about classic AP Katarina go here - Your AP Katarina Du Couteau Resource

Greater Mark of Strength
It's a really good boost to your abilities and helps in last hitting minions.
0.95 x 9 = 8.55 AD

Greater Seal of Vitality Greater Seal of Vitality
I realized that you need some more HP until you buy Rylai's Crystal Scepter.
Badass HP per level! lawl

Greater Glyph of Warding
Since the best lane for Katarina is mid, it will help you against AP carries.
1.34 x 8 = 12 Magic Resist

Greater Glyph of Strength
Gives you 1 AD since you have that 0.75 left from quints!
0.25 AD

Greater Quintessence of Strength
Boosting your abilities some more and making your basic attacks stronger.
2.25 x 3 = 6.75 AD

STARTING ITEMS:

Boots of Speed
This is a great starting item if you're playing against champions that uses skill shots to deal some damage to you, like Kennen or Lux.
Also good against champions that can't deal damage to you if they are not right next to you like Garen and Nasus. Also if you get this item buy 3 Health Potions!


Doran's Blade
You can start with this item if you want to play offensive early, but it's not providing you any sustain in lane so it's maybe smart to pick Teleport to run to base when you're low. Also buy some Health Potions too if you don't have money for either Bilgewater Cutlass, Hextech Revolver or even early Hextech Gunblade!

CORE ITEMS:

Hextech Gunblade
Massive boost to Katarina's Bouncing Blades and Death Lotus!
It gives you every single offensive thing: Spell vamp, Life steal, AD, AP and Active (dealing 300 magic damage and slows the target champion by 50% for 3sec, 700 range and 60sec CD). Since we are not picking Exhaust as summoner spell when you turn your ultimate on, use active from Hextech Gunblade to slow down the target so it can't run away while you are preforming your Death Lotus.
I GOT A TEN MINUTE GUNBLADE AIMED AT YOUR HEAD !


Sorcerer's Shoes
Increased damage on your abilities, works great with your ultimate!
Almost any boots works on Katarina, like Ionian Boots of Lucidity and Berserker's Greaves for critical strike Katarina.


The Two Bloodthirsters
So you can deal tons of damage!
This is the base damage item that you will buy in the game, it provides you 100AD and 20% lifsteal when fully stacked. So when you buy the first one farm as much as u can, because that is how you get stacks on this item.


Maw of Malmortius
You get AD and bonus AD that is based on your missing health, works great for AD Katarina since you are facing AP carries! Shield that absorbs magic damage will save you sooo many times and that magic resistance will be more than useful!


Rylai's Crystal Scepter
Gives you a decent amount of health, a lot of AP which increases your damage some more.
And I know that this item isn't ad but slow on your abilities works just amazing with Katarina, we can't ignore that.

FINISHING ITEMS:

Guardian Angel
As finishing item because you are Katarina and you are always focused in fights.
Gives you tons of armor and some magic resistance, and great passive!


Quicksilver Sash
Buy this item when you have Mordekaiser, Vladimir, Nasus, Malzahar... in enemy team to counter their abilities. Activate item when they throw some of their abilities on ya. It provides a lot of magic resistance too.

CRITICAL STRIKE:

Infinity Edge
If you want to play critical strike katarina focus on your basic attacks more.
This is your base critical strike item that you will get, gives you crazy amount of damage!


Phantom Dancer
First of all it gives you critical chance and it also:
Works great with Infinity Edge and amazing amount of AS and movement speed!

Voracity

This is one of the best passive abilities in the game, it makes you a great tower diver since your Shunpo is refreshed when you kill the enemy. Also in the team fights if a lot enemies died and you are still alive, you will probably be able to throw one Death Lotus on the start and on on the end of the fight!


Bouncing Blade

Use this ability to last hit minions and poke the enemy champion. We will max this first early since those two things are really important until you get your ultimate. It scales with both AD and AP, gains a little bit more from AD.


Killer Instincts

This is the ability that will give a decent boost to your Bouncing Blades, Shunpo, Death Lotus and basic attacks.
Healing reduction for 5 seconds on Buncing Blade will counter a lot of champions like Swain, Dr. Mundo, Warwick and you can throw it whenever someone uses Health Potion. Other effects like damage reduction and increased damage are not that important.


Shunpo

This is the best ability in your set! It allows you to jump on champions, minions, monsters and wards. It's like a free Flash, so it's sometimes smart to have a ward in your pocket so you can set a ward over a wall and jump on it while enemy is chasing you. It also deals nice damage but it scales only from AP. This is the second thing you want to max because of CD reduction and increased damage.


Death Lotus

This is what makes Katarina so powerful! She goes into "eat face" mode for 3 seconds while she is throwing daggers and ripping your head off. Well it's similar to that...
Only bad thing about this ultimate is that it can be stopped by simple stun, knock back or knock up! So in the fights wait for the enemy to use their CC and then jump in with your Shunpo and turn on your Preparation and then Death Lotus. That will probably ace enemy team.

Tested a lot of combinations and this is the one that you deal most damage with, usually the target is dead after this combo.

- When your ultimate is not in range anymore and target is still alive, try to chase it a little and throw your Bouncing Blades!
- If your Hextech Gunblade is on CD and you don't have Rylai's Crystal Scepter or Exhaust it's not so smart to jump and turn your ultimate on.

Early game:
- You can start with Boots or Doran's Blade. If you have enough money for Health Potions, buy them.
- Poke an enemy with Bouncing Blades and last hit minions with it too.
- Play defensive until lvl. 6, you will loose most of the fights until you get your ultimate!
- Buy wards when you can so you can go back when enemy jungler comes to gank you.
- Let the enemy push your lane if your jungle wants to gank and possibly kill the enemy.

Mid game:
- If you won your lane and got the turret gank other lanes as much a you can.
- Help your team get dragons.
- Don't chase enemies through the map, you can get baited easily!
- Farm farm farm farm...

Late game:
- In the fights be sure to be the last one who will initiate, because you want for enemy team to use there CC before you turn on your Death Lotus!
- Help your team getting baron and push lanes, be sure to have your team around so you won't get caught!
- If their team starts going offensive be sure to protect your turrets with someone beside you, never protect turret in 1vs4/5! In those situations just leave it.