Welcome to my Katarina guide, I'm a very professional katarina player and I mastered her enough to make a guide on her!
It took alot of time but now I can even beat my own counters easly :)
Well this is my first guide in mobafire so try to enjoy and I'd love to get some feedback :)
enjoy! :)

Pros

- No mana
- Safe from ganks thanks to her Shunpo
- Very mobile champion
- Great roams
- Great farmer
- Very High Burst Damage
- Alot of AoE Damage

Cons

- A bit of CC and her ult is gone
- Very squishy
- Get focused alot in team fights (so you need zhonyas for sure)
- Has alot of very hard match-ups in lane

So basiclly in the early game you wanna harass your opponent with your Bouncing Blades

Basic harass combo on your enemy is Bouncing Blades > Shunpo > sinister steel
do that only if you feel confident to not get harass back.

For an example dont do that on a Kayle because she will just heal herself, slow you down and destroy you with his Righteous Fury

But for another example you can do that to a Talon because if he tries to harass you back he will run out of mana and you are pretty much gonna win the trade.

The Bouncing Blades > Shunpo > sinister steel combo is the best harass combo in lane because after you use ur Bouncing Bladesthe next spell does more damage, after you lane your Shunpo you take 15% less damage, and when you use ur sinister steel on enemy champions you get some movement speed so its easy for you to back off quickly without taking much or any damage at all.

In the early game, try to not waste your Shunpo if you are pushing the lane, because you'll need it to escape from ganks, if you're getting ganked just Shunpo to a minion or just place your trinket near your tower and Shunpo to it quickly.

If you're oppponent is below 50% health and he can counter your ult, so try to make him waste that abillity, like Talon's Cutthroat and then just jump on him like that:
Bouncing Blades > Shunpo > sinister steel > Death Lotus > Ignite
and you are most likely gonna get the kill! :)

If he can't counter your ult immedietly like Fizz or Swain so just feel free to go on them, because like on Fizz, it takes time untill his Chum the Waters goes off so meanwhile you can destroy him with your ult, just dont forget to make him waste his Playful / Trickster before you go all in on him.

And of course if he cant counter your ult at all like Lux Morgana Karthus
feel free to all in them anytime :)

So as soon as you get to level 7-9 something like that you can start roaming, the best lane to roam is the bot lane, just tell your jungler to hold your lane while you go roaming and you should be fine, make the enemy think you backed off, and then you're gonna be in the bot lane and they are just not gonna expect it! unlesss they have tons of wards so try to avoid them if you can.
when you get to the bot lane you wanna focus on the ADC of course, if you have a Leona or Thresh or anything with a bit of CC you should be able to get at least 1 kill very easly unless the guy flashes or something.

If your bot lane is pushed so try to go top, it's a bit hard to roam top because in the curret top lane meta there will be tanky champs with dmg, so its gonna be hard for you because some of them has escape, some of them dont, so again, if you wanna kill someone in the top lane you must have someone on ur team with a bit of cc, that way you can have a bit of chance of getting the kill.
But overall I don't recommend roaming top lane, It's very hard and you're most likely gonna get nothing from it, unless there's a freaking Teemo there.....

So here we are in the late game.. 35+ mins...
so in the late game team fights, you just need to know 1 thing for sure, NEVER EVER jump in first, that's not smart and you are just gonna get destroyed easly.
you have 2 options in team fights:
1. if you have something like Amumu Wukong or anyhting else that fits well with you, tell him to go in first and you'll just Shunpo there and use your Death Lotus get your resets and kill everybody.
2. if you dont have anyone that fits well with you so do this:
wait for you main tanks to go in first, and then jump, or you can go from behind and just Shunpo to the adc from nowhere and just destroy him with your Death Lotus very quickly, then get your resets and Shunpo out of there.
sometimes it won't be easy to do because usually the support will protect the adc in his body, or he will just go into the fight like Leona.
so pay attention to that.
whenever you get a reset in team fight, try to locate the lowest person and try to kill him with your deadly Bouncing Blades > Shunpo > sinister steel combo, which will do alot of damage in the late game.
and that's the best thing in kat, she is an amazing clean up champion thanks to her Voracity

Alright so let's start building her:
you wanna start with Boots and 4 Health Potion every time
unless you know you are gonna get harassed alot so you can start with a Doran's Shield as well

On your first back try to get a Needlessly Large Rod, and if you can't afford it just upgrade to Sorcerer's Shoes for some magic pen and better roams and more mobility.

Alright so the core items on kata are:
Deathfire Grasp Zhonya's Hourglass and Rabadon's Deathcap

You wanna rush Zhonya's Hourglass if there's an AD mid laner against you like Talon Zed Kha'Zix

If not, rush Deathfire Grasp it's an amazing item on kat, gives you so much burst and it's great for 1v1ing.

After the Deathfire Grasp get Zhonya's Hourglass and then get Rabadon's Deathcap

After getting these core items you wanna go for some more magic penetration,
Void Staff or Abyssal Mask,
get Abyssal Mask if there's a heavy AP team against you with alot of damage,
If not, get Void Staff since it gives you more magic penetration and the magic resist that you will get from the Abyssal Mask would be useless.

last item is gonna be Guardian Angel. it's such a great item on kat because if you end up dying in the late game team fights you can just revive and hopefully get your resets back and keep going in the team fight :)

You are maxing Bouncing Blades as it will give you better burst.
Then you wanna max your sinister steel second for more DMG on it.
And max your Shunpo last, really there's no reason maxing Shunpo because it has less damage compare to your Bouncing Blades or sinister steel.
and you don't need the cool down reduction for it because of your passive Voracity
Of course put points on your Death Lotus in levels 6, 11 and 18.

For summoner spells I recommend Flash and Ignite
because Flash is something you need for any champion and Ignite will help you get kills in lane and when you roam, of course you need that ignite if you are playing against a Swain or a Dr. Mundo to reduce his healing effects.
you can take Teleport if you want for more suprise attacks when you roam and getting to places faster but I don't recommend taking Teleport

Anything else is very bad on her.. don't even think of getting Barrier or something like that