I've never build a private range, but I'd love to. However, the gun club I'm a member of has 11 separate ranges for pistols and rifles. Most are approx 30 yards deep, one is at least 50 yds., and two are a full 100 yds. with multiple benches, and approved for h/p rifles.
These are all 3-sided ranges, with just high dirt berms. Big enough to drive your pickup down to the target stands, then turn around and drive out. Park right at the benches and git after it. Clean, clear, flat, no rocks and very few weeds. Great place for scrounging brass! I can always fill up a gallon jug every trip.
Some are double-wide, some are CAS setup, and there's also h/p rifle ranges out to 600 yards, shotgun areas, .22 rifle silhouette, Cowboy lead-only ranges out to 500 yards, Porta-Johns everywhere, it's a nice place!
You'll need, at the least, a tractor with a big enough front end loader to make the berms nice and high. Bobcat ain't gonna cut it. I think my club has a big trackhoe for berm maintenance (maybe it's just on loan from a member). I'd want 'em thick too, FMJ ammo from big rifles can go through a lot of loose, unpacked dirt.
Make sure to remove all the rocks you can, those cause ricochets. If you save your brass, you might consider vegetation control to make it easier to find them.
Good drainage is important, don't want a rutty mudhole. A scraper blade on a tractor would be invaluable, IMO.
I'd also want to make sure it's situated so the sunlight falls on the target/backstop area as much as possible. I hate to shoot with the sun in my eyes, or cooking my face, and it's nice to still see your targets at sundown.
This old dog likes the shade, so a covered bench area would be the shizz, IMO. Walls would help contain the brass too. Nothing elaborate, something like a simple cattle shed would be great, set up to let breezes through.
Sorry to blather, this one one of my favorite pipe dreams.