Check out The Big Book of Quick Knit Afghans by Leisure Arts. They have a few really easy, yet beautiful designs. They are all made with size 17 circs w/ two strands of yarn held together.
This afghan from Leisure Arts' Afghan Medley to Knit is pretty simple too if you know YO and SSK.
Check out Lionbrand's free patterns. The afghan patterns are at the bottom of the page.
Freepatterns.com has some nice afghans; take a peek and see if any are for you.
The afghan in this Learn to Knit book is remarkably easy!! It was the first afghan that I made from a pattern! My finished afghan is proudly displayed on my bed. When I finished it, my mother tried to steal it!! :lol: I took that as a definite compliment!!
As far as the yarn is concerned, you can really use anything you like. Just take the recipient into account; for example, if using wool, be careful to note who's allergic. Or if using an expensive yarn, be mindful of the kind of "life" the afghan will "live" ... would you really want to spend hundreds of dollars to make a afghan for a child who might well drag the afghan around on the floor (or other such frightful afghan abuse!) :shock: And the yarn also depends on the pattern. A lot of patterns call for worsted weight while other call for chuncky. The best way is to touch and feel many yarns. I've only ever used acrylic and there are tons of different feeling acrylics out there. The one I really want to try is Bernat® Berella® “4”. It not in any retail stores in my neck of the woods and I don't like ordering online because of the shipping & handling.
Anyhoo ... Hope that helps! If I think of anymore, I'll let you know...