Hi there , Katarina is one of the best champions and the BEST mid champion. She cost no mana while casting an ability. She has a passive that lowers her cooldown of skill so you can cast a skill all time by killing enemies and score triple quadra or penta :)) . you can escape from enemies or catch the enemies with shunpo. She has a multitarget ultimate but short range (I whink it is a good range but pretty short) you can't miss the skills so don't worry :) Use skills in this order : ->->->:)

There are two skills you can farm with theese two skill's names are Bouncing Blade and Sinister Steel Katarina's all skills cost no mana so you can cast them all time for farming.

lvl 1:buy boots of speed and 3 health potions. Farm farm and farm
lvl 2:Farm
lvl 3:when you buy hextech revolver you can start pushing and killing :D
lvl 6:now your ultimate is availible :) :) :)
lvl 10:now you can kill everyone easily with ulti and you can kill them without ulti too
lvl 13-14-15-16-17-18:You can kill them easily without ulti and score pentakill with ulti very easily

In early game you will be able to kill them but they will try to kill you too they can't so they will try to escape. Say someone in your team to go alone wait for them to attack and attack them "PENTA KILL" :) In team fight fust us your Shunpo to get the middile of them and cast your ultimate You did it again "PENTA KILL" :)

Born to Noxian privilege, Katarina trained in the ways of the knife from the time she was a child. Now that fiery, willful child has grown into a beautiful and deadly woman. Katarina's intense passion for life is tempered by a sense of duty and loyalty to her family. That same passion proves a double-edged sword when her heart and her responsibilities are at odds.

As the free-spirited daughter of a prominent Noxian general, the young Katarina was given the best of everything. Naturally gifted in combat, she found herself drawn to blades. Much to her family's pride, she trained under the deadliest assassins in the Noxian military. It wasn't long before Katarina's instructors deemed her worthy of a trial by fire - to kill a prominent Demacian soldier. Creeping through the darkened military camp, Katarina was overwhelmed by her passion to prove herself. When the army's General strayed across her path, unguarded, she quietly slit his throat. Katarina disappeared into the night, pleased with her impressive kill. Her elation was soon crushed, as the next day her original target - the prominent soldier who was the true military genius - led his forces to ambush unprepared Noxian soldiers. Katarina flung herself into the fray to correct her mistake, earning a scar over her left eye as a permanent reminder. Even though she finally completed her task, her family's reputation was damaged. Since that day, Katarina vowed to never let passion prevent her from bringing glory to both Noxus and her family. Reconciling her desires with her duty proves to be a constant challenge. To the world, Katarina is a symbol of Noxian patriotism, though there is more to the red-haired assassin than meets the eye.

''Never question my loyalty. You will never know what I endure for it.''
-- Katarina

With using this guide you will have so good scores

Voracity After a kill or assist, Katarina's cooldowns are reduced by 15 seconds.
Bouncing Blades
Katarina throws a dagger that bounces to the 4 closest enemies, dealing 60 / 95 / 130 / 165 / 200 (+45% of ability power) magic damage. Each subsequent hit deals 10% less damage. It won't bounce to hit the same enemy again on the same cast. Enemies hit are marked for 4 seconds. Katarina's basic attacks or spells will consume the mark dealing 15 / 30 / 45 / 60 / 75 (+15% of ability power) magic damage. Total magic damage dealt, including mark consumption, is 75 / 115 / 155 / 195 / 235 (+60% of ability power).
Sinister Steel
Whirls daggers in a circle dealing 40/80/120/160/200 (+0.6 per bonus Attack Damage) (+25% of ability power) magic damage. If she hits an enemy Champion, Katarina gains 12 / 20 / 28 / 36 / 44% Movement Speed for 1 second.
Shunpo
Katarina moves to her target's location, appearing behind it. If the target is an enemy, she deals 60 / 85 / 110 / 135 / 160 (+40% of ability power) magic damage to the target. After using Shunpo, Katarina gains 15% damage reduction for 3 seconds.
Death Lotus
Katarina throws a flurry of blades, channeling for two seconds and sending up to 10 daggers at the each of the 3 closest enemy champions dealing up to 400 / 500 / 600 (+ 3 per bonus attack damage) (+175% of ability power) magic damage over 2 seconds to each champion. Daggers that are thrown apply Grevious Wounds, reducing healing and regneration by 50% for 3 seconds.

CC = Crowd Control (Stun, fear, slow, snare, etc)
AP = Ability Power
AD = Attack Damage
MPen = Magic Penetration
CDR = Cooldown Reduction
OOM = Out of Mana
HP = Health/Health Points/Hit Points
DoT = Damage Over Time
AoE = Area of Effect
MRes = Magic Resistance
CS = Creep Score
MS = Movement Speed
DPS = Damage Per Second

You will be best with going to mid but you can be good with other lanes too

The altarnative runes you can use are:Greater Mark of Insight
All of Katarina's abilities are dealt as magic damage, and as such you want magic penetration. This extra MPen is very helpful along with your masteries (if you follow my setup), your Sorcerer's Shoes, and the MPen from the Void Staff in this build. All of the MPen will allow you to slice through enemies as if they had virtually no MRes at all, even offtanks and tanks.

Another viable rune option is the Greater Mark of Destruction. I enjoy taking these runes on a lot of my APs since they only take away 3.5 magic pen, which is hardly noticeable, and add a whopping 9 armor penetration, which helps a lot for auto attack harassing and a bit with last hitting as well. However, I prefer these on ranged champions since you harass a lot with your auto attacks when you have the range to. With Kat, though, most of your harass comes from your Bouncing Blades and other spells, and more often than not you detonate your marks with Sinister Steel or Shunpo, not auto attacks. However, you still DO attack, so if you want to take these, you can.
Greater Seals of Vitality
With these, it is quite an easy choice. Besides these being half the price of the flat Greater Seal of Fortitude, they give around 4 times as much health at level 18. Scaling Seals of Vitality also have a larger amount of total HP per rune turnover once you hit level 5, which, since I mid, I hit quickly, and even side-laning you hit quickly. Flat HP seals are only really helpful for jungling, since they only grant more HP really early game, and we are not jungling with Kat in this guide :)

You want health seals to make her a little less squishy. In total, 9 of these seals give around 180 extra health at 18, which helps a lot considering you don't have to spend any gold in-game to get the extra HP.

The HP also acts as extra effective armor and magic resist when using your Shunpo, since you take reduced damage from ALL sources.

You could also go with the Greater Seal of Resilience if you notice the enemy is physical damage heavy (if playing draft mode). Armor seals also help you take reduced damage if you draw minion aggro, and most AP mids harass often with auto attacks -- having armor seals mitigates a bit of that damage. I still prefer HP/level seals more often than not, especially in Kat's case due to the effective resistances, but these are a good alternative.
Greater Glyphs of Warding
These runes help a ton. You get 12 MR in total from the start, and since you will most likely be mid, this means you are negating quite a bit of damage from the enemy AP's spells, which helps a lot early on to let you lane longer. I get flat over scaling here since the scaling Greater Glyph of Shielding becomes more effective at level 9; however, by then, you will have some more health and tankiness anyway, from your items as well as naturally leveling up, so having a bit more MR won't be nearly as effective as having a large amount early game. You need to make sure you stay in lane and do not get pushed out early, since that can set you far behind and put your enemy way ahead. The larger amount of MR from these flat runes over the scaling ones early game help you achieve that.

If you happen to go mid vs a non-magic damage dealing champion, you can take the Greater Glyph of Force instead, which will give you a bit of a boost to your total AP.
Greater Quintessences of Potency
These quints are great. Right off the bat, you start with 15 extra AP (not including masteries), which adds around 11 more damage to your Bouncing Blades (including the mark detonations), 9 to your Sinister Steel, 6 to your Shunpo, and 26 to your Death Lotus. This is nice for early game harass, and lets you farm a little bit easier as well. These quints have more of a drastic effect early game, when the extra damage from your AP will really show in ganks and harassing, but through late game, in conjunction with Deathcap's passive, it will turn in to around 20 extra AP. And, going into a game with free AP, without having to spend a single gold coin, who DOESN'T want that? These calculations do not include the total AP increase from the Archmage mastery points.

I get these over the AP per level Greater Quintessence of Force because those only give, together, around 9 more AP. And the extra AP gained from them does not pay off until level 12. Now, if you are mid, you might think "oh, well he said the other per level runes were okay if you are mid," well these are different. Their early game effect is SO drastic, and this also lets you get boots instead of an Amplifying Tome first thing (see "Items" section for more on this), that you want to get flats.

Other viable alternatives could be the Greater Quintessence of Swiftness, since the extra movement speed helps a lot early game for mobility and juking enemy spells, and the Greater Quintessence of Transmutation, which would give you a free 6% spell vamp off the bat, which would stay with you throughout the game, increasing your vamp from 20% to 26%.

This is the end of my guide. That is the best guide untill you find better .Thank you for looking, rating and using my guide enjoy your game...