Gates are fine on drum and some instrument mics, finding the right threshold, hold and release times so the gate doesn't sound like hitting the mute button is the input channel is the trick. Also don't go overboard on the gate depth (how much it turns down the input) 10 to 15db is good in most cases.
As for gating vocal channels well don't. By the time your get the threshold high enough to the drums and stage volume out of the vocal mics you most likely will be gating the vocals to some extent depending how the vocalist work the mic.