How Do I Get Items For A Shop?

Hello everyone!
I'm glad you clicked on this thread, as I need some help. I'm not really all that sure how to collect good items that people want to buy. I have a 40%-ish loot bonus on my main class, yet all I get are unique items with terrible ids, along with the occasional rare, that is still far surpassed stats-wise by legendary equipment. I see so many shops with lots and lots of items. Do I just need luck, or do I need to grind a lot more? Or is there another way?

Sorry if this is a noobish question, I'm still somewhat new to the forums.

 

Mobs, loot chests, daily rewards, etc.