Ignite and Flash...the standard Katarina spells...ignite for killing for easily and flash for trolling or diving. :D

Try to harass early game with your Q while farming with W. You can also shove waves with Q W at level 13. Last hit if possible because you REALLY want to hit 6 before your enemy does.

Pros:

UNGANKABLE WITH SHUNPO

No mana so spamming abilities.

Very strong after Lvl 6.

Too much burst.

Cons:

Hard early laning

Any midlaner with CC can counter her ult

Really hard game against harassers

You should be aware that when your ulti hits Rank 2 you are a BEAST!!! Especially if you have Gunblade and Liandry's you are almost UNDEFEATABLE. But you must know EXACTLY when to go in a teamfight. If you go too early, you will be focused and killed. If you go too late, your team will die without you. So you should go AFTER the biggest amount of CC has been landed on your teammates. And when you kill the first guy... Resets and resets and resets and PENTAKILL!

After you have mastered Kat as a midlane assasin and you can defeat every single matchup you can first pick her in rankeds.BUT remember there is always the chance of enemy team going JAX PANTHEON DIANA VAYNE LEONA...personal experiences...If you are not first pick you should see what enemy summoners pick.If they pick something safe for you you arewelcome to take pentakill. But if they pick counters dont just say YEY IM KAT MASTER I CAN DEFEAT EVERYONE. Always be humble...and when you can ask the support to be Morgana...very good synergy (morgana black shield kat, kat go 1v5)

I usually take my Q at level 1 and most times just max it but against some melee laners like Akali Yasuo and Zed i max my W because it provides me the movespeed and of course you can just spin around every 4 secs dealing great damage and farming efiiciently too.