Better Homes and Gardens has a basic sewing book which shows you many techniques. Got to learn to sew a seam before you can make your own. :)

I’d say start out with commercially made patterns, just to learn how to sew. Then start altering them.

There are some good books on pattern drafting and draping. I forget the names, but try looking at local schools that teach classes on it, and get a hold of their book list.

Good luck!