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

Try to get sorcerer's shoes fast as you can then haunting guise then some spell vamp (hextech revolver => Gunblade) then you can pretty easily kill/harass your opponent

When you think your blade will last hit minion/s and your opponent just use Q or only auto attack