We bought this 2-pack of canvas drop cloths at the Home Depot. They were $10 for the pair. We liked these because they were a little more gray than tan.
Some of the other canvas drop cloths were only 1 in a package. The ones we bought were perfect because we needed 2 curtain panels.
We bought a Queen size flat sheet at the thrift shop it was on sale for $3.
Snip the sheet at 4" increments and tear apart. (Do this the long way so you have enough length to ruffle.) We used 6 strips per panel. Adjust depending on the size of your curtains. The combination of the warn, softness of the sheet and the tearing gave the ruffles a nice vintage edge.
After the strips are torn, cut the hemmed edges off the strips so they are raw on all 4 sides. Sew a gathering stitch down the center of the 4" strips. Gather.
Adjust the ruffle to fit the width of your panel. Pin the gathered seam along the pencil line. Continue pinning all 6 ruffles. Sew a straight stitch over your gathering stitch. It's a little awkward because the drop cloth is a little thick.
Once you have sewn the ruffles on, they are ready to hang!! You could easily make a pocket at the top if you don't want to use curtain clips. We bought our clips and rod at Target.