It all depends on the time period, the social status of the person, his rank, and what the hell he was wearing at the time before he became a pirate.
But first to answer your question "ive always wondered if pirate reinactors, fans etc wear tight pants or baggy ones."
Since very few of the people who do pirate impressions are what I would call actual reenactors, you see a whole plethora of leg coverings, from knee breeches to slops to sweatpants to kilts. Noone has any standards and if you try to point that out they probably just stare at you in slack-jawed incomprehension or find some suitably "pyratical" thing to say like "yarr...me wears whatever me wants, yo ho me hearty, eh what?" So in other words: wear whatever you damn well want and no one will care one way or the other.
Now having said that, if you want to be accurate that requires a little research. Pirates had no uniform. Hell, the most navies had little or no uniforms for common seamen until well into the 19th century. As such pirates and seamen wore essentially nautical civillian clothes. For simple seamen back to the middle ages, most of them wore what we call 'slops' of very very loose fitting breeches or trousers that were most usually made of canvas or leather and often worn over nice, under breeches. This was to protect the nice breeches from stains, tears, etc. As the 18th century progresses breeches themselves become more and more fitted as waistcoats become shorter and frock coats more cut away to reveal the legs. Earlier in period the legs close by means of ties, later on in period they close with buttons, although styles varied widley from country to country.
On ships shoes became useless and as such were quickly abandoned along with stockings resulting in sailors often going about barefoot, though they would presumably change back into shoes and stockings when not on board the ship.
Of course, this is directed at the more working-class level seamen. Officers such as surgeons, navigators and so on who were not required to do as much manual labor could often wear fancier clothes and could keep their shoes. Hope that helps.
