Hi my name Is Mitch and I like this game, and this champ, and dealing metric butttonnes of damage, Many people disagree with my play style for Kat but I just roll with it. any questions comments or suggestions are welcome. Enjoy

Pros
-Crazy damage
-No mana, can spam forever
-Cleanup after fights like no other
-Strong ganker
-Great Mobility
-2 second creep clears
-Really fun
-HEXAKILL

Cons
-Kinda squishy
-shut down by most disables
-Lower damage early game
-May require a more durable start
-ult can be interrupted by allies....I'm talking to you Anivia

I like to take all the magical damage masteries I can and only take to Armour penetration so that I can get havoc. I go for defense over utility due to your need to be toe-to-toe in team fights.

Ability power Quints for maximum damage (think of them as a free Doran's ring)

Magic pen marks for even more of the damages and to semi counter magic resist stacking.

Magic resist seals due to the fact that your enemy laner will probably be a mage. Switch for health or Armour if needed(for AD mids etc.)

Armour glyphs for AD mids and late game durability, switch out for health AP or scaling of either (I recommend flat because a good start will make scaling less important.

Best summoner spell in the game. Flash in to initiate/chase, Flash out to escape. I recomend this on every champion.

Use to snag early kills, falls of a bit late game, but useful for the grievous wounds, use on the enemy LS/SV/HR stacker to shut them down.

I like to think that no item build should be the same in two games. Always pick and choose your items carefully. My point is you can pick and chose from my list of items or choose your own, I recommend all AP items for Kat except for archangels and sheen, no mana and the way Kat is played doesn't allow for time to AA. Also AD items really boost your ult like crazy, just keep that in mind.

Magic resist can also be considered core because you will be the target of most disabling spells(which usually deal magic damage) I recommend abyssal scepter or mercury's treads.

Keep at least one ward on you a ward jump (Shunpo to a ward) can save your life!


ACTIVE ITEMS:
Death Fire Grasp the enemy health stacker or Magic resist stacker.
GunBlade when chasing or 1v1ing
Zhonyas to dodge the big abilities of the enemy or for an extra 2.5 seconds to wait for cooldowns in a fight.

Your text to link here...Wardsto Shunpo over walls just E to a ward. Also use for vision.....Duh. Place around Baron/Dragon, buffs, brush, etc. DON'T BE STINGY WITH THE WARDS!!!
Also I recommend you have a ward in the middle of your lane as an emergency E target.

Your Passive is what makes you the best Clean up champ in the game. you can jump in, deal tons of damage, get a kill and repeat.

Your Q is very useful for both laning and harassing. When I play Kat this Ability is almost always on cooldown, I spam it constantly. This skill should be maxed first but can be postponed for levels in earlier sinister steel. Take at lvl 1 to harass/ catch far away creeps you would otherwise have missed.

Sinister steels is a totally spammable AOE that should always be on cooldown. Much like you Q it should be used for harass/disengage and farming. Take it at level 2 to help blow up the marks form your Q, could be gotten at lvl one if going up against an enemy melee or skill shot reliant champ (to dodge skill shots with the MS boost.)

This is what makes you such a versatile and elusive mid laner/assassin. You can use this offensively to deal damage and avoid 15% of it in a trade. Also it can be used defensively for dodging enemy skill shots and taking reduced damage from inescapable ultimates, Imagine you have a Karthus ult on you, i would Shumpo to take reduced damage and maybe save my life. Another defensive use is to ward jump over walls or out of the way of bid ults....I'm talking to you Lux and Ziggs. I recommend you have a ward in the middle of your lane as an emergency E target.

Your ult is one of the most fun, annoying, and counterable spells in the game. It deals crazy damage to up to 3 enemies and reduces their healing. Since this ability has such a short cooldown feel free to use it to harass or just get off a bit more damage in a trade. Keep in mind that it is shut down by almost EVERY DISABLE IN THE GAME. this is why it is so important to know the abilities of the enemy team. Wait until their disables are used and then go in. Keep this in mind in late game team fights, because an ult that is stopped early will seriously lower your teams DPS.

I put some notes with the skill build. Kat's skill build is pretty flexible just don't max Shunpo first.

take Sinister Steel at lvl 2 to help trigger your Q marks and to harass/disengage.

Shunpo can be taken at lvl 2 if you want to dodge more

Shunpo can also be taken at level one if you really feel at risk of early ganks.

Kat is very good at poking. Use a good old QW combo for quick damage/disengage or a QWE for a guaranteed escape. Also QEWR works because your ult has such a low cooldown that it can be used just for some quick harass.

Constantly dodge enemy skill shots with Shunpo

early game last hit with your AA and Q from afar. when using your Q try to time it to jump to your enemy.

Mid game QW to clear entire waves with some AP

As the mid you have dibs of the wraith camp, however make sure that taking it won't screw up the junglers pattern or put him/her behind.

TLTR

AA/Q farm
QW to Clear
Take wraiths but be considerate of the jungler

As Kat I recommend you get boots of travel and gank relentlessly. You will build a huge advantage for yourself and your team, Just make sure to coordinate with you team properly through chat and smart pings.

KNOW THE ABILITIES(particularly disables) OF THE ENEMY TEAM
keep track of what they can use to stop your ult.

1.wait for enemy disable cool downs
2.Throw out a Q
3. Shunpo in and W
4. Use your death lotus
5. Get a kill/assist
6. Rinse
7. repeat

I hope this helped, I also recommend you spectate others and watch YouTube spotlights on Kat to get a good feel for her. If you can try to trade for her in Aram, the constant skirmishing will make your team fighting as Kat godly. Best of luck out there!
GL;HF