Focus on Your Armory and Staff Store
When you first gain access to your Castle in Fire Emblem Fates, make sure to build up your Armory and Staff Store first. You’ll want to be able to buy weapons, staffs, and Seals for upgrading your character classes. Save the more entertaining facilities like the hot springs for later. There’ll be time for that once you have a good base of operations going.
As you progress in the game, you’ll also be able to upgrade those stores so that they’ll stock better weapons. Building and upgrading costs 1 DP each, so make sure to get those out of the way before you start looking into other facilities.