cant shift into 2nd gear

Hi well my problem with my 1994 bmw 318i is i cant shift into 2nd gear. So i have to start off at 1st gear and then shift into 3rd gear. What can be the cause of this happening. i think its the synchronizer, maybe the gearbox. i dont know but i wanna fix this as soon as possible. Also how much do u think it might cost, because if its the transmission having problems i more than likely will replace the clutch with a whole new one. Thank you :)