If you are going to use your smartphone, get a 2 amp car charger/usb charger. Malakas kumain ng battery yung gps + data connection 1 amp will still drain your battery.

I use waze for metromanila, di ko sya napakinabangan sa province. Although I appreciate its ETA feature.

I also have MapFactor, free and offline but not that user friendly especially sa search ng lugar. But I used it on our trip to baler, ok naman.

Havent fully tried Osmand yet, maybe on next out of town. It can be used offline

Finally Google Maps and Local, although di pa gumagana navigator sa pinas, it can still plot your route and so far reliable naman ang google sa search ng place. Also appreciate the Local app of google, where you can search the nearest establishment you need, like searching restaurant or ATM in an unfamiliar province.