Clothing was very expensive in the ancient and medieval world, because without engine-powered machines cloth was very hard to make. So most people had very few changes of clothing; many people probably owned only the clothes they were wearing. Many children had no clothes at all, and just went naked. In the Stone Age most clothing was made of leather or fur, or woven grasses. By the Bronze Age people had learned to spin yarn on a spindle and to weave cloth out of the yarn on looms. Although many clothes, especially coats, were still made out of leather or fur, most clothes were made out of wool (from sheep) or linen (from the flax plant) or cotton. Some rich people wore silk. In the Middle Ages (the medieval period), people invented the spinning wheel, which made spinning yarn go about four times as fast. Clothes were a little less expensive than they had been before, but still most people had only one or two outfits.
Around the Mediterranean, in Egypt and North Africa and Greece and the Roman Empire, people mostly wore wool or linen tunics (like a big t-shirt). Women wore long tunics, and men mostly wore short ones. Over their tunic, they might wear a wool cloak, if it was cold. Further north, in Europe, a lot of men wore wool pants under their tunics - as you probably do today.
But in India and Africa, people mainly made their clothes without sewing, out of one big piece of cloth wrapped around themselves in various ways, like a woman's sari in India, or her kanga in central Africa. Most people's clothes were made out of cotton or silk.
To find out more about ancient and medieval clothing, check out these books from Amazon or from your library:
Eyewitness: Costume, by L. Rowland-Warne (2000). For kids, but mainly European clothing, from earliest times to modern.
Dazzling Disguises and Clever Costumes, by Angela Wilkes (2001). Make your own costumes - here are directions written for kids!
Clothing: A Pictorial History of the Past One Thousand Years, by Sue and John Hamilton (2000). Includes Africa and Asia, but only as far back as 1000 AD. For kids.
World Textiles: A Concise History, by Mary Schoeser (2003). For adults.