I did similar last year. Made a spot for a 36x60 building, somewhat cut into a sidehill, and additional material imported from 600 feet away. I have a JD 3720, 44 hp 4400 lbs with loader and ballast. As said above, part of the trick is to get it level, and the other trick is to actually have it compacted properly. As I went thru this, I eventually bought a self leveling rotary laser for about $250 recondtioned from CPO. Before I got the laser though, my procedure was:
Move material for the afternoon ( a few hours), spreading it in thin layers and driving over it with the tractor. Put away the tractor and drog over the garden hose and lawn sprinkler. Turn it on for the evening, turn it off just before bed. Come back in the morning and when the mud was gone and there were puddles, spray paint a line around the puddles. Later in the day when the puddles are gone, fill the spray painted outlined low areas with fill and compress with the tractor. Start again with a general lift of fill across the entire area. Each lift was only a few inches across this big of an area in my case.
Repeat.
Its amazing how close it will end up for you.
Choice of what you fill with is important. Rock would be best. In my case, I was ripping out an old overgrown driveway in aonther area, and using that fill, so it had a lot of rock and was mixed with dirt. It compacted wonderfully. Dirt alone would not bear the weigh of wall foundations later. Clay would be worse. If you have to buy rock and mix it in, do so.
Later on, as I started needing to be accurate and work alone on foundation forming, I needed and purchased the rotary laser. I don't know how I would have gotten along without it. I use it for every large project now. Best tool investment I ever made. CPO (online) sells new and reconditioned tools of every kind. Sometimes the prices are very reasonable. Watch their webiste, inventory changes.