My runes that i choose are meant to give me that little bit of an edge when it comes to ability power, i just go straight up power and magic pen because it will allow me to get kills early game.
I dont get survivability runes because health runes become less powerfull later inthe game and i have a sufficient amount of health from items at that point anyways
When i first got katarina i started with bouncing blades because i was still a little cautious with her and that is fine for new players because it is a safe way of getting some early damage, but since i am really comfortable with kat i get shunpo first.
I either get killer instincts at level 4 or 5 because i find that i dont really need it until i use my death lotus.
First things first. DO NOT TOWER DIVE AT LOW LEVELS!!!!!
this is the worst thing for katarina to do since she is a squishy character, once you get areound level 8 or 9 is when you can even start to concider diving for a quick kill.
As you become more skilled with katarina you will find ways to cheat tower diving a little bit by jumping in with your killer instincts on (making sure you get the kill, may need to use bouncing blades) and then from the kill with the CR quickly jump to nearby minions or allied champions. DO NOT JUMP TO ENEMY CHAMPIONS! after towerdiving you life is going to be low and it is most likely they have all of their abilities ready to kill you. if it is necisary use flash to get away.
Start with some boots and health potions because it will allow you to stay in a lane for a long time early game, since katarina is a little squishy early game the health pots fill up her health easily.
Next focus on getting a hextech gunblade, the ap and physical damage is nice and it is very useful early game with the slow and damage.
I play katarina very situationally at this point, if you need some MR then abyscal scepter would be nice, or if you are fed enough get rabadons death cap, but either way get a blasting wand as quickly as you can because it will help you sooooo much in the laning phase, then by the time you get fed enough with your items the game will be collapsing into mid. now you are going to need some health or you will be the target of all 5 people on their team because you are squishy. go for a crystal scepter because it will give you the edge you may need in a team fight.
When it comes down to the last item i usually go with something situational, like in a recent match i went with the soulstealer because i was racking up a lot of kills by then. But you can go with another rabadons if you just want to deal out damage, you might just want to get a void staff though because by late game the other team will be stacking magic resist and armor.
Laning Phase/ Gameplay/ Tips
Early game it is important that you dont feed because it will come back to haunt you later on.
Dont be afraid to spam abilities to get a kill or get away, Katarina uses no mana so all she has is cooldowns which get to be low enough to spam all the time.
One way to harrass at you tower whenit is pushed is to shunpo in and fight for a second and shunpo out.
Dont let a tank at low health fool you into towerdiving, they usually have CC and you will die to a tower.
I go with Exaust and Flash because they are just good spells for laning,
I mainly use exaust when i have an ally around because it often results in a kill for my team or i use it when someone is trying to tower dive me and i need to survive.
I get flash because it is just a good spell to use. i use this for every champion except for when im playing a tank support.
Something else you can use is ignite but i dont see much use for this because your shunpo has a bigger range and if they get to far you can flash in.
If need be you can get ghost but it is not the absolute best thing for katarina, ghost is useful for getting past minions when you are being chased or if they have a lot fo slows on their team but i can usually survive by using her tricks (shunpo) and spamming to get away from whoever is chasing you and being able to outrun them
Teleport can be a good choice if you think you might need to get around the map quicker, when katarina starts getting fed she can quickly turn around a gank and get a couple of kills in the meantime.
Any other spell can be used depending on your personal oppinion
DO NOT GET CLARITY lol
With masteries i go with a little bit of survivability while also getting exaust and flash because those are the spells i use the most, i also get some AP and magic pen so that it is harder to counter my attacks.
Utility is not the best thing to invest heavily in for katarina because she will most likely not be jungling a whole lot and utility is aimed for jungling so they can get ahead
Well i hope you liked my guide, please comment on what you think about it. and please vote after you have played by the guide