So you've probably found or crafted a Topaz Ring or something similar and are wondering what this "Adornment" stat is all about. I'll break it down for you: Edit
1.) Every point of Adornment reduces the price you pay when you purchase items from a merchant by 0.33%, Yes, that Diamond Ring with +3 Adornment (the highest for a craftable item) reduces prices by exactly 1%.
2.) Prices reduced less than a full gold coin round to the nearest coin (up or down). At low Adornment levels you're going to need to be buying a really expensive item to see a difference.
3.) Adornment does not affect how much money you get when you sell items to merchants. It also doesn't affect buy-back prices -- you always pay the same amount as you got from the merchant when you first sold the item.
The unfortunate takeaway is that, unless you're buying something for hundreds of gold, it really isn't worth bothering with Adornment items in the current build.