I use FairEmail. For GMail access, you'll need the APK from Github and not the FDroid version. With this, you won't need any play services.
I like Organic Maps, though it does suffer from routing issues. Without local knowledge (i.e. most of the time as satnav is useful) it could be a problem. I tried it on some local routes and it suggested some inaccessible roads, yet the same routine on OpenStreetMaps worked fine. Obviously the app is still being developed and I imagine that these issues will get resolved.
Magic Earth isn't FOSS.
This leaves OSMAnd, which doesn't have the best UX at times but has fewer routing issues, for me.