There are various shops that can be built that will sell certain goods: some essential for battle, others for apparel. In any shop, items matching the proficient weapon of the person manning the shop will be discounted, so check for those sales!
In the armory, you can buy local weapons and tombs of the region. As you level up your armory, you gain access to more goods, and can buy more copies of limited goods. A 5% discount is applied to the weapon type the person manning the shop is proficient with.
At the Rod/Staff Store, you can buy local staves or rods, dragon and beast stones, and general purpose items such as healing potions, Tonics that boost a character’s stats for one battle, and Seals for promoting units and changing classes! Only rods and staves will go on sale, so stock up whenever a healer character is manning the shop!