Honestly, all I have to say is that you can basically do whatever you want on kat, as long as it helps your team. Play safe and focus on farming early, but if you think you can get first blood at level 2 or 3, go for it. Beware of other assassins bursts, because kat is not the only assassin with a strong level 2-3 burst. When you hit level 6, start looking around the map for roams. For more information, read the notes on runes, items, and champ matchups.

Sorry that the champ matchup section has so little information, I honestly haven't played kat enough in ranked against people that are actually good at their champion, so I feel like the information would be unreliable. Pretty much the same thing for the synergies section.