My suggestions would be to start in the field on your quad, and lay out the track while your riding, that way you don't have turns too tight, make sure that you have a nice flowing loop, run it in good so you can clearly see it. Once you have that done you'll be able to see where the jumps will fit. Build mostly table tops, they take more dirt but are much safer, especially while you are getting the lips and landings right. After building a jump hit it a couple times, If you go to high, tame the lip down, if your not going far enough then lip it up.
Hauling dirt is a pain and its a very slow process. Try scraping the ground around the jumps to get your dirt, it will be much faster.
If you need more ideas come check out the tracks at the proving Grounds.
Hope this helped some.
If you get overwhelmed and want to hire someone to build it for you then send me an email. I do build private tracks on the side. I've done over two dozen tracks. The average 5 acre track will cost about $5 grand. A small investment to have a professional practice track at your house.
Dan Harris #584 Owner/Operator, Breezewood Proving Grounds Inc.
www.breezewoodprovinggrounds.com