Shops

Shops are generally the most plentiful source of powerful non-unique items in the game. They reset on a 24-hour cycle; this doesn't mean that they reset at exactly the same time every day, but rather after 24 hours with something that seems a bit more complex on the surface than it actually is once you understand it (if you just wait a full 24 hours via the inn every time then you won't have to think about it anyway). One way to explain it might be to describe it as follows:
-There's a spell called "Reset Shops"
-It has a 24 hour cooldown
-When you open a shop, you cast this spell if it isn't on cooldown

While there isn't literally a 'reset shops' spell, functionally it's similar.

There are many types of shops, with some being crafters that you may buy items from OR craft some of your own items with (such as the enchanter), some being strictly shops (like the general store on Hammer Island), and one or more crafting-only (like the potion lady on Hammer Island). They all buy/sell slightly different sets of items, as well. In Aventurine (the big main town in the center of Fallowfields, which is the mainland that you sail to from Hammer Island), for example, there are two shops at one of the top-left path against the cliff that sell mainhand and offhand equipment for your class (if you joined an active session you may need it to reset before it shows items from the correct class). The higher one being expert/master tier, and the lower one being apprentice/adept tier.

(input full shop list from https://steamcommunity.com/sharedfiles/filedetails/?id=3021525707 here later)