I read the other day Gaia is supposed to be good, can download map tiles to the phone, covers numerous countries and free version (limits the number of tiles you can load at once I think)…not tried it yet.
alani, MMtracker uses memory map files loaded on the phone so free if you have the maps already (free version of app is function limited). mytracks, endomondo etc use online maps (google maps) so need data connection but free if you have data included in the phone package, just a pain if in the wilds and the signal is poor. Gaia uses free downloaded files so is fine off line.