I agree with Rhoidie, 45ACP Dot and Patrick, trigger control first. I have seen people shoot targets accurately (at 25 yds) with a loose one handed grip. Accuracy is in the trigger control.
Speed is in the grip i.e. - getting the gun back on target rapidly, so grip second.
Edited to add - (There are other things that go into shooting fast, my thought is that they are third after grip.)