KATARINA.. something. Forgot her last game, but whatever. If you are a Kat player looking for a new build, then just buy those items and destroy the enemy team. If not, continue reading :D. By the way.. I have 1130 elo........ time for a new account.

Passive : Voracity - After a kill or assist, you gain 25 extra gold and your cooldowns are reduced by 15 seconds.

Q : Bouncing Blades - Use this to farm early game and mid game whenever you see available minions that are low. On champions, use this to harass if you don't feel like shunpo-ing.

W : Killer Instincts - This skill is very useful. It has a passive(deals extra dmg) and an active(Makes bouncing blades apply Grievous Wounds on targets and you take reduced dmg for using shunpo).

E : Shunpo - Katarina's main damage. Free flash. Use it to escape ganks or when flash is down, shunpo to a ward. Use it continuously during a teamfight because of your passive. Nuff said.

R : Death Lotus - OP skill. Low cooldown. Off cooldown after 3 kills or assists and usable twice during a teamfight. The people who stand in this are basically screwed.

Kat's combos
Harassing : W -> E -> Q
Killing : W -> E -> Q -> R -> Ignite
Teamfight : W -> E -> Q -> R -> E -> E -> E -> E -> E -> E forever pentakills.

Here is one thing that you should know before playing Katarina this way :
STAY OUT OF FOCUS!
Go in the teamfight after they are low, which GAREN-TEEs(Demacia?) you at least a double kill (Quadras and Pentas are very common when played this way).



That is all. :3 Guide might be extended if needed.
Leave constructive criticism, pictures of your scores with this build, and remember to vote :D.