BackCountry Navigator is an excellent application for off-roading. It's available for IOS and Android devices. You can pre-download map content into the application for the area that you'll be traveling to. Then you don't need an active data signal for maps to work while out and about. Your GPS signal will continue to work as long as you can see the sky - the trouble with applications like Google Maps is that they require data connectivity for maps to move with you, because you're actually viewing maps through the web instead of on the device itself, so this application overcomes those challenges if you plan ahead.
The application itself has a one-time purchase price (I don't remember exactly what I paid, but it was under $20). Then there are countless map resources available depending upon the area you're traveling - some are free, some ask for a donation, some cost money outright. I typically use the CalTopo maps, which are free, but also limited and sometimes outdated, as most were created by the USGS some 30 or 40 years ago. The cool part about that is that you can see old mapped features that may not exist on modern maps, like old buildings and airstrips, and go find and explore them. I've also purchased a land boundaries overlay that shows you BLM, Forest Service and Private land boundaries within whatever map you're looking at. I think this was like $8 or something.
I'll warn you now that it's not a super intuitive application. You should read many of the tutorials and tips and tricks as you're using it, as it'll help you get the most out of it. There are also a few videos and articles online about how to use the application.
