Diatomaceous earth is only effective when it's dry and it's only effective against insects.
It won't have any effect on geckos (although if insects are getting into a dry part of your circuit board and you put diatomaceous earth in there it could help).
We live in a tropical environment just like Hawaii and we use Diatomaceous earth inside where it's dry...on window sills to stop ant invasion and on a tray around the pets feeding bowl to stop
ants and other insects.
It's really only useful outside in the dry season.
There are other pest control solutions for the tropics.
Desmodium (a nitrogen fixing legume and ground cover) and other fragrant herbs like Thai Basil planted in amongst your edibles can help confuse pests.
Look up "push pull farming" to get an idea of how effective a simple ground cover like desmodium can be at confusing pests.
Also mulching with a grass like lemon grass or citronella grass helps deter some pests too.
Having a complex multi culture of different species with plants spaced randomly everywhere also helps (instead of putting all your edible plants of the same type in a big row where the pests of that plant can go along breeding and eating).
Chickens, ducks and quails can also help if managed well.
And just staying on top of infestations early on with high value crops using simple methods like knocking pests into a hot
bucket of
water to kill them.
You only have to kill
enough pests early enough to stop out of control reproduction and destruction of your plants so the predators of those insects can do the rest of the protection for you.