There's no oil boom in Oregon. I'm sure there's some turn over of private campgrounds along the coast, but probably few new ones.
The hidden gems that only the locals know about are dispersed sites in the National Forests and BLM land. Directions will be like: FS40 to FS4001, 14.5 miles, turn off on to a narrow dirt track and go 100 yards to a clearing littered with a fire circles and burnt out tin cans.
Everything else will be documented, if not in the RV guides, then on the relevant FS and BLM web pages. And of course on the Oregon state park site.
One loop trip around the state in a mini-RV (SUV setup for camping) I stayed at (starting in the far NE corner)
FS Hells Canyon overlook near Hat Pt
FS near Halfway (found on Delourme Atlas)
Lake Owyhee State Park (very popular lakeside)
Leslie Gulch (BLM) (gravel access, but suitable for big RVs)
Jordan Valley (lightly used RV park in small town)
Page springs BLM (popular with birdwatchers) (ok for rvs)
Harts Mtn Wildlife refuge (remote)
Summer Lake Hot Springs (commercial, on map) (ok for rvs)
(west of US97)
FS near LaPine (ok for rvs)
FS near Diamond Lake (very large popular)
dispersed site FS Applegate Lake (near CA border)
FS on Gold River (having crossed on Bear Camp rd)
Cape Blanco State Park
small FS on OR 138 (again near Diamond Lake)
FS on Metolius River (Camp Sherman area)
dispersed site near Barlow Wagon rd (Mt Hood area).
I made heavy use of the DeLourme Atlas book (Benchmark is equally good). I also had a couple of backroads guide books. And some sites I found just by looking around once I got the area. I also did a lot of online reading before going.