What is the best FX layout for the master bus?

Hi all I am looking for some advice as to what's the best layout of effects in the master bus is. For example is it best to have the gate before the compressor then the EQ or what. Also is it wise to use a compressor on all buses i.e kick drum, bass, Hi-hat & so on. 

Thanks Just one more thing how much headroom should you leave on average on each track?

Headroom on each track is only important insofar as what they all add up to on the master bus. If you end up with 8 to 12 db headroom on the master, then your tracks are fine. If you end up higher than that on the master bus, you won't have much wiggle room left for mastering, so you may want to be a little more conservative on tracks in the future. Most of the time you'll be OK if your individual tracks peak at -12db or less, but there is no hard rule. And it's easy to simply turn the tracks down until you're hitting the master bus at around -12db or so.

You'll usually have as little processing as possible on the master bus itself. What you stick in there depends on whether you're mastering in place or if you'll be sending your song to someone else to master for you. The latter is recommended if you have commercial aspirations, but most of us are hobbyists who do our own mastering. In that case, you will probably have an EQ followed by a limiter. In some cases you might have an additional compressor in between the EQ and limiter. But if you're going to be sending the song out for mastering, you might not have anything at all on the master bus.