However, if those types of details aren't relevant to your story, you don't have to dig into them. My Merging Worlds Trilogy takes place in one country with no widespread traditional dress. Research into different types of clothing is a way for me to know what else is out there besides what I see everyday. It gives me a broader range of clothing my characters can wear. This research also brought to mind natural and man-made materials used to make clothes.
Here are some useful links to help you with clothing in your world. If you're on Pinterest, there are many boards for clothing from around the world. Also, if your fantasy country is similar to one in our world, you can Google "clothing in France" or "clothing in South Africa", for instance. Or, you can do a Google image search for, let's say "culture and clothing" or "clothing from around the world."
National Geographic: Photo Gallery: Global Fashion
Pinterest: Around the World: Traditional Clothing
Pinterest: Clothing of Different Cultures
Pinterest: Traditional Clothing Around The World
BBC: Costume Gallery
Cultural Fashions: A Study of World Culture and Fashion
Wikipedia: Clothing by Nationality
Science@home: 13 Traditional Costumes from Around the World
Wikipedia: Clothing Materiel
Types of Clothing Fabrics
Textile School: Types of Fabrics
...On an unrelated note, you've probably noticed that Goodreads Giveaway widget at the top right. You can enter to win 1 of 5 advanced signed copes of my upcoming book The Sciell! Giveaway is open now until February 21. Check out the widget to enter.