If You Sell It They Will Buy…
All in game merchants can be broken down into three types. No matter where you are on the map, they are the only ones you will find although they may look the same from time to time. You will be able to tell merchants in the game because they are always beside wagons, carts, tents, or market stands. Also there will be an icon right over their head that will alert you to the type of merchant that they are. To buy from a merchant you merely click over the merchant and bring up the panel.
The Traders – Categorized by the icon of a bag of money this is a general store and will carry a basic standardized selection of trade goods.
The Blacksmith – Categorized by double swords icon this is a store that will specialize in items that Hunting, Warfare, or Rogue mastery characters will use.
The Arcanist – Categorized by an icon of a spellbook, this is a magic store that spell casters and other lore loving characters will use.
Items available to buy are weapons, armor, potions, rings, dyes, and pendants. There will also be a tab that is called the Sell Back, where you can sell your items to the merchant for cash. Taking items that you find that you do not need and selling them to local area merchants is a good way to make extra funds so that you can afford other items in the game. However if you sell something and decide that you really want it, you can buy it back for the same price that he bought it from you if you haven't closed out the window. Closing out the window and reopening it again will make the stock prices change so keep that in mind if you accidentally sell something to a merchant that you decide you really want.
While the Merchant screen is up, you can hover your arrow over the items that you are interested in with your mouse. Hovering over an item will tell you all about the item, its price and its attributes. If you are a going to be looking at things that are similar to items that you already are equipped with, it will bring up a comparison checklist so that you can easily see its stats as compared to ones that you have.
When you are ready to buy, you can just click on the item. If you are able to afford it, meaning if you are having enough gold in your possession to purchase the item, then it will be yours and go into your inventory.
Keep in mind that the stock that the merchants carry isn't static, and it will change over time. So if a merchant doesn't have what you need one day, always check back and see if they do later on.