Pros:
-Insane Burst
-High Mobility (Great Roaming)
-Strong Mid-Game
-Fun to Play
-Attack On Everyone Ultimate
-Snowballs when ahead
-No mana
Cons:
-Squishy
-Very hard to play and master
-CC can be a problem

Flash This is the standard spell for anyone besides Vladmir, Olaf, and Singed, who don't always take it.

Ignite The wonderful provider of first bloods, cheap kills, heal prevention, burst damage, and so much more. I feel like I'm selling you all a product, well I guess Ignite is officially a product, used mainly by assassins or aggressive non-junglers.

Barrier I've actually seen this work form time to time, however it doesn't work even close to as well as [ignite], though it has a shorter cooldown. It is perhaps a good summoner spell for beginners to League of Legends who are trying out Katarina

Cleanse I mean I guess I could see this being taken if 4 or 5 champions on their team have extremely hard CC, eg. [orn] top, [Malzahar] mid, [sejuani] jungle, and a [varus] and [alistar] botlane.

Domination

Electrocute
We take this because it is strong for bursting people down and works well for first bloods. We want damage, and this provides just that.

Taste of Blood
Not many of us takes this but i do since it gives decent healing, and i like this over Sudden impact.

Eyeball Collection
Works well for our Mid-Game spike, and besides Zombie Ward has been nerfed, and Ghost Poro is next to useless.

Ravenous Hunter
It's actually a cool idea, but we would rather have CDR but if you are interested in trying a more lifesteal build you could choose this and Taste of Blood

Triumph
This is a great tool for getting hp back in the middle of a team fight, if you wanna be more tanky go with Bone Plating

Coup de Grace
This is an amazing tool to finish off people under 40% HP, since it gives an extra 8% dmg on them. otherwise go Second Wind for the extra sustain.

Passive Voracity
INNATE: Whenever an enemy champion dies within 3 seconds of Katarina damaging them, her Cooldown reduction icon cooldowns are reduced by 15 seconds.

Sinister Steel
SINISTER STEEL: Whenever Katarina retrieves a Dagger, she uses it to slash through all nearby enemies, dealing 68 - 240 (based on level) (+ 100% bonus AD) (+ 55 / 70 / 85 / 100% AP) Ability power magic damage and reducing Shunpo Shunpo's Cooldown reduction icon cooldown by 78 / 84 / 90 / 96%.

Daggers last 4 seconds before disappearing.


This is where all of our late game damage comes from. It is also what Katarina is based around, if you are able to properly maneuver and set them up.

Q Bouncing Blades
ACTIVE: Katarina throws a Dagger to the target enemy that bounces to up to 2 nearby enemies, dealing magic damage to each target.

MAGIC DAMAGE:
75 / 105 / 135 / 165 / 195 (+ 30% AP)
The Dagger then lands on the ground 350 units opposite from where it struck the target.

The time to land from striking the target is the same regardless of distance traveled.
This ability is a fun one and there is a reason we max it. We can bounce this off of minions or off of champions in lane to set up daggers for Shunpo. It can do a bit of damage, but the main purpose is the blade.

W Preparation
ACTIVE: Katarina tosses a Dagger into the air above her current location and gains a decaying Movement speed icon bonus movement speed until it lands after 1.25 seconds.

BONUS MOVEMENT SPEED:
50 / 60 / 70 / 80 / 90%
Chasing someone down? Use W. Want to dive or go in on an enemy in lane? Use W. It can give u good AOE damage in teamfights as well.

E Shunpo
Katarina moves to her target's location, appearing behind it. If the target is an enemy, she deals 15 / 30 / 45 / 60 / 75 0.5 total attack damage 0.25) magic damage to the target. If cast on a dagger, or walking over one refunds 78 / 84 / 90 / 96% of Shunpo's total cooldown.

This is the essence of Katarina, it is how you outplay opponents, how you escape and stick with champions, it is your everything. It allows you to have insane mobility, whilst allowing for strong lane all ins and engages

R Death Lotus
Katarina throws a flurry of blades, channeling for up to 2,5 seconds and sending up to 15 daggers at the each of the 3 closest enemy champions dealing up to 375 / 562.5 / 750 (+ 3.3 per bonus attack damage) (+285% of ability power) magic damage over 2 seconds to each champion. Daggers that are thrown apply Grevious Wounds, reducing healing and regeneration by 50% for 3 seconds.

Insanely busted as long as you don't get CC'd you will be able to get a lot of damage. AS SOON AS THEY LEAVE IT YOU NEED TO CANCEL IT AND FOLLOW UP. This is the only way to be able to maximize your damage because otherwise you're just sitting there doing absolutely nothing while waiting for the full channel.

VS.

These 2 items are the only 2 starts that really have success, I have found Long Sword simply not to be as effective. Dark Seal start is a popular start on Katarina as it provides extra healing from potions(and more Health Potion), along with having better snowball potential due to additional stats. Doran's Shield start is also a safer option, that still allows for aggressive play. I have found that you should start The Dark Seal in matchups where you know you can dominate them. The Doran's Shield is safer and more reliable, so it is especially good for those learning Katarina due to it giving additional health, health regeneration, and even extra damage to minions, which is useful when last-hitting.


Hextech Gunblade
This is the single target burst damage that every Katarina main yearns for. AP for abilities, AD for auto-attacks, and a active that does a bunch of damage. It does more damage then Hextech Rocketbelt and provides us with the stats that we want. It is always our first item and is usually completed just after level 6.


Sorcerer's Shoes
This is where our first MP comes from and it helps us eliminate all basic magic resistance enemy champions have while providing us with good mobility, I sometimes complete this before Hextech Gunblade if I have 1100 (or 800 if you start Boots) gold on first back.


Morellonomicon
This is our lovely healing prevention, which happens to also provide some magic penetration and tankiness. With this we can survive for longer while pumping out loads more damage, I have found myself getting this as my second item more and more often due to the resurgence of Dr. Mundo, Soraka, and Vladimir in the meta.


Rabadon's Deathcap
The AP champions item. This is simply all we want as an AP champion so long as we have our other AP items this can be a good 3rd item, though it also works as a 4th one.


Void Staff
This is an item we like to purchase early on in our build because it provides us with the proper magic penetration to begin really bursting down carries, I have been starting to use this over Morellonomicon as it has a better effect on the game due to the damage output.


Zhonya's Hourglass
This can be bought vs. Champions like Zed or Fizz who have ultimates that you can use it to dodge such as, Chum the Waters. It can also allow you to survive in precarious situations and to dive into a team and come out of it alive because it gives your team a little bit of time to engage.


Liandry's Torment
The burn damage of this is very fun allowing kills that shouldn't have been possible, it also provides some more health allowing you to survive for a slightly longer time.

Katarina's playstyle has always been an aggressive one where you attempt to snowball out of control through lane kills and proper roaming. A lot of the time even when she is getting dominated in lane she can still have a major effect on the game due to her quick and easy botlane roams which commonly result in 2 free kills for your team. You will want to play her around fights around dragon, due to that being when she is most powerful. Once baron fights start to occur her power will be less effective, but if you snowball your lead properly with the Lawnmower Strategy you will easily win the game. The "Lawn Mower" strategy is basically where you and your team get a kill in a lane, take it's outer turret, and then rotate to the other 2 lanes' outer turrets. You then procede to do the same to the Inner Turrets, etc. This is the best way to finish a game where you can't just send all 5 players to steamroll the midlane right through their nexus. Currently she is a pretty strong champion, however with electrocute nerfs, she is disappearing from the meta.