I think as a beginner quilter, you would find it much easier to start with fabric, rather than with clothes. I have found inexpensive fabric at Wal-Mart and that might be a good place to start...or with a 40% off coupon at Hancocks, plus Hancocks often has fabric they are clearing out at good prices. I have only cut fabric out of clothing a few times, and I found it very frustrating to cut out the sizes I needed.
One easy pattern that really looks good is from Missouri Star Quilt Company....though they have videos on lots of easy patterns....but the two slice layer cake makes a really good quilt. (Just google Two Slice Layer Cake quilt pattern...if you are interested.) They start with a layer cake (42 ten inch squares of fabric from one line), but you can start with any fabric, cut it into ten inch squares, and go from there.
Let me find a picture of one I have made, in case it interests you. I used five fabrics in the last I made and liked it a lot.
Dina