When I first tried Katarina before her rework, I couldn't use her at all. For some reason I just couldn't get her down right and I ended up being the weak link in any team. This is pitifully sad since Kat is actually one of the most deadly champs I've seen in the game through streams and various vids on her.

When they did her rework I tried her again, still I couldn't use her at all. I just didn't get how people were owning with her so hard. Yes she can be item dependent but most champs are. So, I left her alone for a while and focused on just improving my over all game play.

Recently I decide to try her again just for a change of pace and absolutely destroyed. It shocked me to the point I thought it was just a fluke so I did it again, and again, and again. She works so well for me now I was very happy I spent the IP to buy her so long ago even though I thought I wasted it on her due to my own playstyle just not meshing well.

Turns out that her skill cap is just a bit higher than most champs is all. Really and truly an extremely fun champ to play if you can get her down and get her farmed. The snowball effect on her is probably one of the highest in the game.

One thing I need to learn with her is escapes and harass, her burst is nice and all but if you don't play it right you can put yourself in a very bad spot very easily.

From what I've seen, and how I've played her I learned 2 things are very important with her.
1: Don't got all in unless you know 100% you can kill your target or that it's 100% a 1v1, a jungler can spoil a take down and reverse the outcome quicker than you can say "Oh snap".
2: Save your E if at all possible, it's a good way to make skill shots miss and sometimes it's your only method of escape.

Her ability to play cleanup crew is absolutely key. I never initiate a fight, I never jump into a fight right away. I always hang back (hopefully out of sight) and go in once I find the right target or an easy kill to jump on so that my skills CD auto-refresh and on to the next target.