This is where I ask again "What do you want to do?" Optimising requires a goal. A class is not a goal. Using a sword isn't a goal.
Do you want to do as much damage as possible?
Do you want to be as survivable as possible?
Do you want to protect others?
Do you want to build on the spring attack you can get from warrior poet?
Do you want to switch flexibly between your gun and katana?
Do you want weird tricks?
Do you want to humiliate your enemies?
etc.
I'd misremembered warrior poet - while they can get some abilities related to spring attack, they don't get spring attack itself as a bonus until 6th level. Assuming you're willing to be building towards that:
From fast hero get defensive martial arts and personal firearms proficiency. +1 AC is +1 AC, and being able to use a gun may matter sometimes.
From warrior poet get the flourishes kitsune's mystique (move and feint, improved feint for free) and exodus of Jinin (+10' speed). You also get weapon finesse for free.
From levels & human you have a choice. Get combat expertise, weapon focus and swordplay style for a defensive approach, or power attack, furious focus and combat reflexes for a more offensive approach.
Later feats to aim for are things like swordplay upset (5th) or weapon trick (5th), chain challenge (7th) or whirlwind attack (7th).
Yeah, and it works with fast hero too, though either way that's another build that won't be fully ready at level 4.