
Do you want to make a quality build, where you invest an equal number of levels in strength and dex to give yourself access to a wide range of weapons? Or do you want to favor Dex or Strength? That in turn will influence how you infuse your weapon. Lkewise, a Heavy +25 Uchigatana has a scaling of A in Strength.

A Keen ("sharp") +25 Uchigatana has a scaling of A in Dex.

However, this assumes a standard infusion. But according to the Fextralife entry on the Uchigatana, once upgraded to +25, a standard Uchigatana has a scaling of D/C, making it slightly better for Dex than for Strength. In Elden Ring, the Uchigatana has an initial scaling of D/D for Strength and Dexterity, respectively. These denote the weapon's attribute scaling, from E (very poor scaling) to S (very good). When inspecting weapons in your inventory, you should see letters below the stat requirements. Invest in either Strength or Dex, depending on the types of weapons you want to use.

Around 40 Vigor, you'll have ~1400 HP, which significantly increases your chances of surviving against most mobs. It's around 30 Vigor that you begin to see a better return on investment from pumping points into health. Your top priority should be to get 30-40 Vigor to increase your survivability.
