I recently finished a weeklong overland trip through AZ using the following setup:
1 - Older iPad Air 2 with RAM Mount/Owl Expedition Media Mount.
2 - Dual Electronics XGPS160 GPS Receiver ($140
Amazon). I tried to get my iPad to read locations from my iPhone 6 and it seemed to work at home, but not when I was off grid. I decided not to take any chances and went with a device that I knew would work. The receiver worked like a champ, but you do have to monitor the battery. I started out with it on the dash, but eventually just left it on the passenger seat. It might even work in the rooftop sunglass holder, but I did not try that.
3 - Gaia GPS 5-year Premium Membership. Here is a link for $128 for the 5-year Premium Plan.
Lifestyle Overland Discount | Gaia GPS It's actually less than I paid! Having the Nat Geo maps alone is worth the upgrade, but I also use the MVUM and even the wildfire history maps to see which areas to avoid. I live in the Southwest and have even used the satellite images to see where the trees are to help find good camping spots.
I followed a route that somebody else had outlined by importing their GPX file, but it is easy to create your own routes. While not turn-by-turn navigation (ala Siri), the setup followed right along as I was driving and I was able to easily tell if I was still on track or if I had missed a turn. I was able to drop pins and photograph good campsites in case I come back to the area.
The only drawback to using a system like this is that you have to download the maps before you leave or from a wifi/cellular source while on the road. If you decide to do some off-route exploring and have not downloaded a sufficiently large area, you will run out of map. This wasn't a problem on this trip, but I carried paper FS and other maps anyway. There is a limit on how many map tiles you can download, so you have to play around a bit with the zoom level and the number of layers you want to download. On your home PC there are no limits so you can use all the resources you want to plan your trip. I spend a lot of time "armchair exploring" before going out!
There definitely is a learning curve, but I have found tons of videos and info on how to use the system. Even the list of map overlays available is overwhelming, but I have about 5-6 "go to" map layers that I download.
Please note that I am in no way affiliated with any of the parties mentioned above. I love Gaia GPS and have used it may years for hiking/biking, but only recently for overlanding.