Although the Philippines, in general, is not a tipping culture the practice is becoming more common. Rather than trying to work to any complicated formula, I usually just tip a flat PHP50 – 100(~USD $1 – 2) to cafe and hotel staff and PHP200 (~USD $4) at upscale restaurants. This is more than you will find as the recommended amount in the various tourist guides but, to a typical Westerner, PHP200 is not going to be missed whereas it is a meaningful amount to Filipino hospitality workers who earn low wages even by local standards. When using Uber, Lyft, or taxis I always tip at least PHP100 to my driver, regardless of how short the trip may have been. While fares (and, hence, driver earnings) are scaled against the local economy, local fuel prices are more representative of those found in the West, not leaving much margin for drivers.
As a final note, if you forget to tip or choose not to, you won’t be treated to a poorer level of service. Unlike some other countries, Filipinos consider a tip to be a pleasant extra, not a matter of right.