Hey Summoners!
My name is Joschua, alias Knirpsipirpsi, and I am from Germany (I Hope you can understand everything I say, If something is not clear please feel free to write me). This is my second guide on Mobafire and I desided to make this Guide for my main Champion in LoL, Katarina. I play LoL since season 3 and I'm GoldV in this season (6). Katarina is my favorite champion, so I thought about sharing my experiences on her with you. I hope you have fun reading this guide and think about playing Kata aswell!

Why should you play Katarina? Here are the Pros and Cons:

Pros:
+Recourless Champion
+Easy to learn
+AoE Ultimate with huge Dmg
+Good and easy Farming
+Strong roamer
+no skillshots
+Hard Snowballer

Cons:
-Bit weak early game
-Not usefully if she isn't fed
-Ult easily interrupted
-Squishy
-No CC in her kit
-Melee

Your first Summoner spell should always be flash. You need it for diving/chasing enemies or getting away from a gank.
Ignite is really good to make your combo a 100% death for the enemy.
Other oppurtunities than ignite:
TP is good vs your counter in lane. You don't lose that much XP in lane and you can TP on Botlane to get some free kills and get ahead in lane
Barrier is unusual but also possible. Its good if you think the enemy backline will snowball (Like Jinx often does)

and 4are my usual start. With this you have good sustain during the laning phase and also you can dodge more spells thanks to your MS. An early Ludens echo will higher your dmg extremely. When you get this Item you have your first power-spike and should be able to start fighting your Lane Opponent.
After Ludens buy AP-Items.
For Boots I recommence the Ap-penetration-Boots, also possible are Boots of speed if you roam much or Ionian Boots. But I don#t think that you will need much CDR due to your passive.

Katarina reduces the cooldown on all of her abilities by 15 seconds whenever an enemy champion dies within 3 seconds of being damaged by her.

Active: Katarina throws a dagger to the target enemy that bounces to the nearest unaffected enemy up to 4 times, dealing magic damage that is reduced by 10% for each enemy hit, down to a minimum of 50% damage, and marking each target.

Katarina's basic attacks and abilities consume the mark on affected enemies, dealing bonus magic damage.

Active: Katarina whirls her daggers, dealing magic damage to all nearby enemies. If Sinister Steel damages an enemy champion, she also gains bonus movement speed for 1 second.

Active: Katarina blinks to the target unit and reduces incoming damage by 15% for 1.5 seconds. If the target is an enemy, she deals them magic damage.

Active: Katarina rapidly spins in place and channels for 2.5 seconds, throwing a dagger every 0.25 seconds to each nearby enemy champion, up to a maximum of 3 at a time, dealing them magic damage and applying Grievous Wounds icon grievous wounds for 3 seconds.

As you I max the Q first, because this Spell is your Main Damage source.
Secondly you skill your E, to have less CD on it.
In the end skill your W.
Many people do their W secondly, to have a shorter CD on it and to deal more dmg. But in my oppinion the E is better. For dmg you have your Q and ult, and aswell the E deals more single Target dmg than your W, which makes this attack better for one-shotting people.

The normal harass combination with her is to use your Q on the enemy, E on him and use the W to pop the mark of your Q.
A combination vs someone who plays on long fights on lane is to Q him, move next to him and pop the mark with your W and immediately jump back to a minion of your wave.
The full combo looks like this: Q, E, W, R, and Ignite when the enemy leaves.
Reactivating your Ultimate will cause to stop it, so if the enemy flashes away with low HP you stop your ultimate and ignite him to let the ignite finish him off.

As you see I use 12/18/0 on her.
The reason why I recommence Thunderlord is simple. Your Q,W,E combo are exactly enough to pop the active of it. So your burst damage is even better.

Instead of the hybrid penetration normal penetration is also possible. Aswell you can take scaling or flat MR in the Glyphs.
Vs AD-Midlaners Armor instead of scaling Health is better.

Thanks for reading my guide! I hope I helped you out in becoming a better Katarina player! I know that my guide isn't the best Katarina guide but it's okay (in my opinion) for average players (like me) so I really hope you liked it!