Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
**note** This is my adaptation of a build shown to me on League craft.
I'd just like to start off by saying, stay with me till the end. Ive used this build for Kat and it works. You gen enough gold to be the first person to get to the end of your build. As soon as you get Rylai's Crystal Scepter and your Hextech Revolver you are nearly unstoppable against squishys if you catch them off guard (and Kat's Shunpo will ensure that). With Kat, you need to pop that ult. Pop it like its plan A1. Her passive will ensure that its up when you need to have it. That said, her passive cant do everything, especially when you just can't get that kill. So I like to save it if I know the mid fights are going on. Also, I usually go top or bot as Kat but this build is just as viable for mid lane.
I was skeptical at first of the 3 lucky pics. But just try it and you won't be able to play without it. They give you enough AP for beginning game, and gives you enough gold to make King Midas blush. The rest of the build is pretty self-explanatory. The Deathfire Grasp may have some mana regen, but it has plenty ap, some cooldown redux and a sick active ability.
If you have any questions, feel free to ask me. Im new to mobafire but ill try to get back to you!
Thank you and please vote :D