Crocheting is my number one hobby. I used to buy yarn online regularly. However, after a couple of bad experiences, I stopped. If you are buying directly from the company, it is usually fine. I went on eBay and bought some a couple of times and didn’t have a good outcome.
The problem that I had was that the picture showed full skeins of yarn but when I received it, it was only half skeins. Make sure before you purchase the yarn online how much you are getting.
Now, I usually go to Hobby Lobby. They have a yarn clearance about twice a month.