If you have to cut parts, I'd keep the brass and reeds, piano and percussion and maybe add a synth for the string parts. The reed parts give the score much of its creepy atmosphere, and the brass is pretty crucial for many of the big moments in the show. That nine piece orchestration though is very intricately written, though, so try to use as many parts of it as you can.
Begin at the beginning and go on till you come to the end: then stop.