Need suggestions - Best places to see big stuff?

[Hike]

Flight from Manila to Palau is expensive but straight forward(3-4hrs).
Check if Cebu Pacific has cheap flight to Kota Kinabalu but you still need another flight to Tawau or a very long bus ride to Sempona. Getting the permit to dive Sipadan is another issue.
From Kota Kinabalu you can also try Layang Layang for the hammerhead.

Check AirAsia, they have flight to many places from Kota Kinabalu and cheap

 

[mrrworld]

A few years ago there were cheap flights to Palau through Davao in Mindanao. Can't remember the carrier but it was a very good deal.

 

[Lasse Nielsen]

Whalesharks are to be seen in Donsol. Oslob is a zoo! I was both places in march 2012, and Donsol was the best experience.
Tubbataha is also great, I saw hammerheads, grey-black-white reef sharks, eagle-manta rays, bumpheads, tunas and much more.
Apo reef is almost just as good.