I tried to purchase an used car myself as a lone expat and found it to be mostly negative experience compared to more developed countries:

It's common not to post make year and mileage. Just saying “I sell a Navara” with no details.
Even if you ask for mileage, and if seller replies you, it doesn't have to be real mileage. One guy told me upon test drive “the number I sent to you is what's shown on dashboard and I've replaced dashboard”.
Many ads turned out to be outdated (no such car), and small shops use it to offer you whatever they may have at the moment.
Overall it took me more than 7 days and two trips to Manila to meet with a dozen of sellers and finally buy a car.

You can try looking at Facebook groups because for many Filipinos internet = Facebook and they rarely open web browser at all.