When they suggest expensive yarns and you just can't afford it (like me) go to the site of the yarn they reccomend and look up the information on that yarn. It will tell you the thickness of the yarn by a number that stands for fingering, worsted, bulky, etc. All the modern yarns that I know of are rated by this scale. There will still be some differences in exactly how the yarn is but it will be pretty close. Remember that higer quality yarn may give a noticably better product but if you can't afford the good stuff, a lower grade will have to do, and you might not even notice the difference. You might be able to go through EBay or yard sales and get the "good stuff" at a really low price, too. Be sure you know if it's a specialty type like the furry ones or lumpy ones, like boucle and if they're fuzzy or smooth. Try to match them up as well as yo can and give it a whirl. You might to try something really different too. Just be sure you keep to the right gauge.