Admiral or Commodore be the look of a Captain Hook, who sports a frock coat plus boots, accessories n' more weapons. He likes to show of his rank with lace, ruffles, metal buttons or brocade cloth.
More of a Capt Jack Sparrow look who also wears a frock coat plus boots, accessories n' more weapons. He practical nature uses simple plain fabrics, more leather and simpler buttons.
Such as 1st Mate or Quartermaster and Gunner.
He wears waistcoat, hat, plus baldric n' weapons with contains lace, ruffles, metal buttons or brocade cloth to show off his success of this pirate adventures.
Powder Monkey or Scurvy Dog just be starting out n’ can only wears shirt and pants plus bandana, sash. Having to do all the hard work, it makes sense to wear rough garb o simple plain fabrics without any adorments.