Luggage and bags:
You will need a daypack to carry around your suncream, insect repellent and camera etc.
An ordinary suitcase is fine for your main luggage, as long as it isn't huge.
Clothing/Shoes/Weather Gear: Long trousers
Long-sleeved T shirt type tops, ideally with a high neckline
Sturdy boots and socks
Waterproof poncho or cagoule (it rains even in the dry season
Toiletries and Medical Supplies: Insect repellent with a high percentage of DEET (e.g. 'Jungle Formula') - don't forget to reapply the repellent to your hands after washing them!
Calamine lotion or other remedy for insect bites
Vitamin B supplement? (I was told that taking this changes your smell so that insects are less likely to bite. I wasn't able to test this, but it's certainly worth a try)
Photo Equipment: Camera with telephoto/zoom lens
Plenty of film or digital storage cards
Camping/Beach/Outdoor Gear: Torch/flashlight