gościu is sometimes used especially to people you are not friends with
yeah, this is neutral... used sometimes when we refer to someone who we don't know.
ziom and variations - ziomek, ziomal, ziomalek, ziomas, ziomuś
dude - koleś or stary
typ - used sometimes in situations like
'ej typie, a wpie$#%@ dawno nie dostałeś?',
'ej typie jak cie tu jeszcze zobacze .... '
there are also some variations of koleś - for example koleszka
also non positive word - leszcz, 'spadaj stąd leszczu!'
if someone know equivalent words for Polish slang that I used here then feel free to translate sentences above.
I would say yes, sometimes, not often used ... it would mean sth like 'old (but current) friend'
'to mój stary ziom' - this is my old friend