When I built my pole garage I needed to build a pad. I used a laser transit and my tractor with a box blade. I have a hydraulic top and side link so that helped a bunch. When do you stop? Who knows, whenever you are satisfied I guess!
If this helps, here is what I was able to do with my 24hp tractor and box blade. The first pic is what I started with.
Since some of the gravel will sink inot the mud, I'd make sure I put in 8 to 10 inches. If that is going to be more than 1 load, and I'll be it will be, start with big stuff and graduate to smaller on top.
I'll add a sand/clay pad for the shed, near the middle of the cleared area(maybe 8 inches) and then gravel on top of that. I'll get by with a string level for now. That rotating laser level sure looks cool though.
I was hoping to work on it yesterday, but real work got in the way. I guess there's always the weekend.
David rotary lasers are really nice tools but like everything the good ones are expensive. The problems you run into with the less expensive ones are that they are not self leveling and the light intensity of the beam can be difficult to see in sunny areas. By the way a simple water level is very accurate and maybe more so that an inexpensive rotary laser when you get over 100'. They worked well on the pyramids.