The entrance to the Lanayru Desert is the best place you can get Tumbleweed early on.
You'll have to run around for a bit, keeping primarily to the middle and wait for the wind to pick up.
Once you see the wind and dust appear, a Tumbleweed will appear and start rolling in the same direction the wind is going in.
You have to be quick, so it doesn't roll right into a wall or some sand, so that's why you should stay more towards the middle so you'll have more time to get it.
Or, if your problem is just how to pick up the Tumbleweed, you need to use the net for that.