As you said nobody really knows how much you need to live in the Philippines as we all want and expect different things.
A lot of foreigners come here with the idea they can live with the same standards as filipino's and they cannot.
One mistake i see foreigners making time and time again is not respecting the filipino culture. They usually end up paying for it one way or the other. When in rome do as the romans do. Although you can bend the rules sometimes
Personally i think if you set a budget of about 50,000 pesos a month it will be enough.