Honestly, from someone who plays a ton of Katarina mid, she's a pretty safe pick against just about any mid laner in the game because she's braindead to play and does so much damage. I'm sorry, but I've played well enough Katarina to know that she's basically freelo in Bronze and Silver and if you lose with her, it's because you got cocky, lazy or both. That or you're laning against Heimerdinger because Heimer dumpsters almost everyone now, especially since tank Heimer with Zz'rot and Banner is so popular.
She's a pretty simple faceroll champion with her resets. The only thing you have to learn about her is the order in which to hit her abilities on the engage. Past that, it really doesn't matter aside from remembering to hit your ignite before they flash away.