It your depends on how complex your costume is. A typical Naruto cosplay can take one-two weeks, but something from KH can take months.
Are you sure there aren't any fabric stores around where you live? It's kinda hard to work out of pre-made materials, unless you want to do really really simple stuff like L, and there are always like fifty L's per con nowadays. >>;
As for who to cosplay, pick someone from a series you like; it makes no sense to cosplay a character who you don't even know. You can also check out the
Cosplay Newbies section on C.Com, they have a LOT of suggestion threads.
Aaand then you can always get commissions online. O: