Katana is a solo weapon and Scales itself with the help of Piercing Arrow. You need some time to ramp, therefore it's recommended to use double big shield in particular Moon Shield with double armors.
Make Katana as fast as possible with the help of Fanny Packs, Gloves and Maneki-nekos.
Oil Lamp gives accuracy that Fancy hits more after ramping up.
For Late Game you want to trigger as Djinn Lamps as soon as possible with the help of Moon Shield, Mana Orbs and Piercing Arrow