I can barely sew, but managed to pull together two pirate costumes. For my daughter, we used checked pants, a white turtleneck, black boots, and a scarf that she already had. I bought a women's vest from the thrift store and pinned back the armholes, making a pleat in the back (to draw in the fullness). I sewed straight down what I'd pinned, and it ended up looking like a frock coat. I also made her a little neck ruffle from some old sheets and a cape from a yard of flannel.
She insisted that our new baby be a pirate, too. I made his shirt and pants from $1 bargain bin fabric. I made a regular stocking-type cap for him and then tacked on a Captain Crunch style brim and glued on a felt skull and bones. It needed trim, so I used cheezy-looking fabric paint.