You get 30 days visa-free when you land. If you plan to stay longer, buy a ticket out dated about 29 days after you arrive. I buy a $16 throwaway ticket from onwardticket.com.

Yes, you need a return ticket. It has to be dated 29 days after you land in the Philippines. I buy a fully refundable ticket from the Philippines to Vietnam. Once I land in Manila, I get it refunded. Within 72 hours before you leave, fill out the Philippine eTravel: https://etravel.gov.ph. It's free. There are scams online that charge you $70 to fill out your eTravel. Welcome, and enjoy. Please post in English next time.

Just buy a fully refundable ticket.

I always get a return ticket for however long I'm staying, it can be up to 5 months. I don't get an onward ticket within the 30 days. Check the immigration website Bureau of Immigration, Republic of the Philippines.

A return is sometimes cheaper than a one-way