I'd say something in the neighborhood of 3:1 gearing (mid to high 70's in gear inches) would be about average, with people who prefer spinning higher cadences or who live in hilly areas running something a bit lower. I live in a flat area too, and 48:16 (exactly 3:1) works great for me. Since you're interested in skidding, I wouldn't do exactly that gear since it only has one skid patch, but 52:17 is close gear-wise but it gives you 17 patches.
I would really only switch to 165mm cranks if you're noticing pedal strike with your current setup or if it's too long for you to spin comfortably. That's more of a personal thing than a necessity.