What should I buy for 3 adults and 6 day stay in Hong Kong İsland ( Sai Wan Region West)

Hello there
I would like to know which one would be cheaper to use for the transportation, daily passes or pay as we go? I also want to include, the bus from the airport to where we are staying, it is a few blocks away from the Sai Ying Pun station. Is octopus card good for all kind of transportations as we want to see the big buddha statue and go all the way up to the peak and plus use the ferries or to go to the other side of the island. What transportations would be better for that?
yous response deeply appreciated. thanks much!