Hi,

there's a basketball league here in Doha where different individuals gather and play, check out http://qsportsleagues.com/leagues/basketball

as for gyms, there a lot around in doha, the one I attend is Al Massa Gym which excellent and has all the equipment you'll ever need. a yearly subsricption will cost around $1250, they now have an offer for $1000/year, I don't know if the offer will still be valid by the time you arrive to Doha.

This is my number +974.55563803, give me a call when you arrive or if you have any other questions.