Vicki, I would stay away from merino wools and the more luxerious fibres until you're comfortable with your technique. A coarser wool is generally better for starting out - like shetland, corridale, etc. Something with an average staple. How much you'll get out of your roving will depend on your technique, the texture of the yarn, how you ply it, etc. But a pound will give you quite a bit. Have you got a niddy noddy yet? That can help you determine yardage once you're done.