We also started out trying to keep the cost down and came to realize that the best places we have camped were free or very cheap. I first try to use
freecampsites.net and go from there depending on the area that we are in. If it's in an area we just want to get through we will stay at a truck stop or walmart as last resort. I believe the only time we have had a reservation was in Moab during a busier time.
If you qualify for the
geezer pass you can cut the price in half at many places like dept of agriculture or blm pay sites etc.
When I use a website like freecampsites I will scout the area first with google earth and street view to see if it's compatible with larger rigs. Sometimes the listing or the users reviews will say what size rigs can access it or how the roads are etc. I sometimes find a place to park and ride my bike in first to see if there is room to turn around and how tight it is. Boondocking also opens the door to how you are set up to camp and what your energy management system is.
So, we shoot for free and end up doing it very cheaply. Iirc last year we paid a few dollars a night average.
Escapees club will let you dry camp at their parks cheaply with water and dump available.