A large shirt, cut off at the sleeves, makes a good vest.
(These adorable pirates are my daughter and son-in-law.)
My black velvet coat was actually a dress (I'm going to guess from the 80's) that already had a flared skirt, satin and lace cuffs, and extra lace around the neckline. I just cut it down the front, added a satin collar (with the original collar lace on top), and added a few gold buttons. It worked great!
This was another activity where we wore our pirate outfits. My husband's boots actually only came midway up his calves. I extended them by using the top halves of sleeves from a leather coat I had thrifted for use in another costume. He just slipped the sleeves on first (inside out), then the boots, then he turned the wider part of the sleeves down to form a cuff for the boots. They worked great!
One event was actually a "trunk-or-treat" activity in the church parking lot. We decked out the back of the van with all sorts of pirate goodies. We even played pirate music from the van speakers. It was a lot of fun!
Costume Tip: Don't be afraid to dye suede. I picked up an awesome "70's" suede coat for only 99¢! It was a natural color, but I wanted it to be darker. So I filled the washing machine tub with hot water and dumped in some brown Rit dye. I added the leather coat and let it sit for awhile. When it was all done, I loved the way it turned out. The embroidery didn't take the dye, so it stayed tan in color and really "pops" now. The rest of the leather was a bit blotchy, but great for a pirate's coat!
Click HERE to see more costumes!