While gambling certainly has it's downsides, it can be a great boost to the economy. The money can then be used to fund important areas such as health and education to improve the quality of life. Gambling, much like drugs, is something that will happen no matter what, so they may as well regulate it and put the money to good use.
Yes, the Philippines should allow gambling. However, the approval of gambling must come along with laws that prevent children from taking part in this activity, as well as educational campaigns that demonstrate the dangers of compulsive gambling to the Filipino public. Otherwise, adults should be allowed to make their own decisions regarding gambling.
The problem the Philippines has with gambling is not the act of it, but the fact they aren't collecting the necessary taxes. There is a negative impact from gambling for a small amount of people, but overall most people will do it sensibly. For this reason they should allow it, but work really hard to manage it and collect the appropriate taxes.
In a country where gambling has been very strictly controlled for such a long time, there is no serious need to introduce an infrastructure to allow it to proliferate now. Gambling centres can have a serious effect on local crime and gambling addiction is a serious and distressing problem for many people across the world.