I recommend for you to bring only the necessary thing. I suggest taking a backpack and for moving around, a belt bag or body bag will do. Make sure to line interior your bag with a garbage bag or any plastic to waterproof the contents of the bag.
You can wear shirt and shorts but you should wear something that will cover your legs and arms when trekking especially in some shrubbery areas where you are most likely to get scratches on exposed legs and arms. While at bedtime, a cotton pajama set is suggested as it covers your arms and legs both from the cold and from insects.
Wear comfortable shoes for long walks and good traction shoes for hiking. Some areas are muddy and slippery, like the rice fields.
Bring a cap for protection against the sun and windbreaker against the rains. Insect repellant or cream for insect bites.
For good measure, medicines for fever, body ache, indigestion, and your other medicines; Lip balm for chapped lips; and some first-aid kit.
Bring umbrella during the month of may, since the weather starts to become unpredictable, it might rain during the afternoons.
Camera, of course, but don't forget the case, to protect your camera from getting wet especially inside the caves. Also in caving, bring a reliable camera with good low light capability, a small tripod may be a good help as well, but not the big one.
Flashlight, you will use that when night descends. There are a few street lamps, so finding your way from the restaurant to your lodging house is hard.
Sometimes you have to bring your own portable water heater. The water coming out from the faucet in the morning is really ice-cold. At mid-day, it becomes bearable. Though some lodging house's room has it's own hot shower.
Bring some cash, though ATM is already available. You should also bring some pillows, crackers, and waters for long travels; and iPod/mp3 for a lots of waiting for jeepneys/buses.
