I'm usually pretty quick, but my horse's gear is very basic (doesn't need any more than he has) and he nearly always has rugs on so he's clean 99% of the time anyway... grooming is more a bonding thing and/or to help him drop his winter coat. I take anywhere from 30 seconds to 5 minutes. If I do a deep grooming, anywhere from 1/2 hour upwards.
For shows, I braid/wash etc at home, so it literally takes me 2 minutes to saddle up and 4 to swap saddles between dressage and stadium phase (at the level I'm at, we usually have dressage then stadium then xc).
But, my horse just has his saddle and a basic snaffle bridle with a flat cavesson noseband, so there are two straps to do up on the bridle and the girth on the saddle and that's it.