Gargoyle geckos come from the island nation of New Caledonia, which is approximately 1000 miles from the east coast of Australia and also ~1000 due north of New Zealand. It is roughly the size of the Hawaiian islands.
Diet: In the wild, their diet mostly consists of arthropods 🦗 but also varies seasonally. During the winter, fresh fruits are not available to them, and they prey on other geckos such as bavayia and the multitude of skink species that live in the leaf litter. In captivity, I do my best to replicate this, minimizing dairy-derived food sources and preferring insect based foods and live insects.
Meal replacement smoothie such as Repashy, Pangea, or Black Panther Zoological, mixed 2-2.5 parts water to 1 part powder, can be offered every other day, for growing juveniles, alternate feedings with gut-loaded, calcium and multivitamin dusted bugs, for adults, offer those who will take them once or twice weekly. Repashy Bugs'n'Fruit is a good place to start, as well as Pangea papaya, apricot, fig, and watermelon flavors. I have also had good success in starting young animals on the higher protein content Black Panther Zoological("BPZ") original, and moderate protein colorbomb flavors. Even if you have just one gecko, it is good to have smaller sizes of multiple flavors to achieve a balanced diet, and to rotate flavors with each feeding.
Housing: I recommend bare minimum 2500 square inches per gecko. I house adults and breeding pairs in 18x18x24" glass enclosures. It is helpful to go to Lowe's and get a piece of glass (that they will cut for you, for free!) to partially (not completely!) cover the top screen to retain humidity. If you have a very small (under 50g) adult, I think a 12x12x18 would be OK. Any larger, I think it is better for the animals to have more space. I use "Hefty Hi Rise tubs" for juveniles over 10g and for quarantining new adults.
Temperature and Humidity: One must simply look to the temperature and humidity of the islands and replicate. Be careful of people who recommend "room temperature" as this can vary widely between households and is not an accurate measurement. Conversely, if you are asking people for help, please do not say that your temperatures and humidity are "good" as this is not a scientific measurement either. "Except for a four- to six-week period of winter cooling, gargoyle geckos require daytime temperatures of 78°F-85°F. At night, the temperature can drop into the low 70s during the warm months and into the 60s during the cool months".Vosjoli, P. D., Repashy, A., & Fast, F. (2013). Gargoyle geckos. Vista, CA: Advanced Visions Inc.
Humidity should be maintained from 60-80%, but ensure adequate ventilation to avoid respiratory problems and mold growth.
Size and lifespan: Gargoyle geckos, if cared for properly, can live upwards of 20 years. Most are 7-10" in length including tail, and weigh from 45-65g. Some are larger, from 70-100g. The largest gargoyle gecko on record was "Large Marge", owned by Allen Repashy, and was around 140g. The current largest known living gargoyle is "Ridley", who is an 120g male owned by Tony Terradas of ROC geckos. Ridley was produced by Kevin Cantrell of Passport Herpetoculture.