About the easiest shelter I know to make is a simple rectangular tarp. If you know how to sew a flat-felled seam then you should be good. I made one as my first shelter. All it takes is a flat felled seam down the center, some hemming around the edges, and some bar tacking of webbing tie-outs on the ridge and corners.
Apart from that I highly recommend Ray Jardine's tarp kit. Not only does it provide you with all of the materials you need at a reasonable price, but his instructions are absolutely unbeatable.