The country I want to visit does not require a visa for a stay up to 30 days. What do I need to do? Just purchase a flight ticked? Do I need other documents from the embassy or something else? Could it be that all I need is my passport and flight ticket?
All you need is a valid passport. Sometimes they require the passport to have a certain validity beyond your date of entry, but otherwise that is all.
For the Philippines, you need a passport that is valid at least 6 months after your intended stay, plus a round trip or onward airline ticket. They have no minimum financial requirement like Thailand, but do have the right to ask you about your means of support while in the country.