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.
This is my second build so bare with me.
The idea behind this build is that with two revolvers,
1. You have a decent amount of ability power.
2. You have spell vamp so Kat doesn't need to tp to base every four seconds.
#2 is key since with my previous build and most builds I see there is no health regen whatsoever. You basically either buy 100 health potions throughout the course of the game or you just return to base way too much. Also, with this build you can suicide nicely.
Grab your boots and three health potions and head out. Pick a lane, any lane. Kat excels at mid but if you're not familiar with how she works then take a side line, or if you have someone who "called mid". You can synergize well with most heroes, although some are annoying to lane with ie. morde as you won't be getting many creep kills, and he doesn't have any sort of CC. Harass, work on creep kills, and if you can get a kill with exhaust and ignite, KI+Shunpo, BB, then do it. Otherwise play conservatively.
[color=greenYour goal for early game][/color]
Farm up enough for 2 revolvers. This is quite easy as they're relatively inexpensive. If you're farming very well, go back when you have 2400. If you're not doing quite so well, or are getting harassed, go back for the first one then save another 1200.
How to farm *If you're new to Kat, please read this. Otherwise skip it.*
Many guides say to take bouncing blades first and foremost. To me, this makes absolutely no sense. Bouncing blade does some percentage less damage with each bounce and has dreadful starting damage until it is almost maxed. Stick with shunpo. It does a LOT of damage to one target, so you're better off using it on heroes than BB and also that means more health regen from your revolvers. I use BB and shunpo to last hit creeps. If you're going for the back line creeps or if you're up against a ranged super harass (ashe) use KI first. They WILL try to hit you after you have used shunpo so the near invincibility that comes with the KI+Shunpo combo will keep you in the lane. Otherwise, keep moving to avoid skill shots. If you're standing still you're doing something wrong. Move around the creeps hitting enemy heroes with a KI+Shunpo if they venture near then run back. Last hit creeps with standard attacks, shunpo, and BB but try to alternate their usage such that one is always up.
Mid game arrives and is where Kat really shines (although her early game is quite strong as well since she is not mana dependent). Walk around the map ganking, getting lizard buffs where necessary. If you're low on health go creep and regain it - with two revolvers you can replenish your health quite well.
Your Goal For Mid Game
Get Rylais and finish your boots.
Kill Kill Kill
Don't Die Die Die
Late game is more of the same. Get your zhonyas. Kill creeps and heroes. With Zhonya's Make sure to put it in slot one and map that to an easily accesible button like F or R. That was you're not scrambling with your fat fingers to try and hit the 1 key while the other team is destroying you. Finish the revolvers into gunblades if you want, although I have rarely had a game go this long.
You are not a tank
You are a DPS who is fairly squishy but has a great escape mechanism in shunpo
if you are playing ranked and they have >2 normal stuns (not ult), pick a different hero or get ready for pain
If your team doesn't need dps pick a different hero or just try a tank build kat. It won't work, but at least you tried.
BB works nice for those pesky healing characters. Combined with KI it will reduce healing by 50 percent.
Use KI when going to a battle thereby reducing the cooldown until the next use.
KI, Shunpo, Ult, Exhaust, Ignite, BB will win games if done correctly.