What do you mean "put a bus on the drums"?
There are a couple of different uses of buses. You can assign the drum channels to a bus for subgroup mixing where you can insert effects (okay for eq or compression but not the usual way to add reverb), or you set up an effects bus and send variable amounts of each drum to it (the usual way to add reverb). Some DAWs have different tools for each, others have generic buses that are defined by how you route things.
With an effects bus you should set the reverb to 100% effect (just reverb return, no dry drum sound) or the channels you send to it will get louder when you add reverb.