Bro I have a friend whos a car dealer. Here's some tips:
Always check the papers if original
If hindi ka maalam sa oto. Bring a professional, wag yung kaway lang sa banawe.
Nothing beats resale value of Japanese Brands, mostly toyota, mitsu, and honda.
Diesel has a lower price, and consumes less fuel.
Manual uses less fuel than automatic, pero if you want city drive, opt for matic ka na.
Innova has 8-10km/l in average traffic manila so thats what I would recomment.