It really depends on how you want the result.
If you want to get orchestral hit you should combine several instruments.
some percussions or crashes.
Sometimes, several wind instruments will be enough.
As for disco, I think several different staccato strings will be ok.
But you need to experiment. Try too combine strings with short organ sounds or some synths.
The main thing - all sounds should be very short. And do not forget to add reverberation.