I would definitely have to disagree. A 12x12x18 enclosure is too small for an adult gargoyle gecko. You need at least an 18x18x18 in my opinion. (I assume we're talking about Exo Terra and Zoomed Terrariums here.) Gargoyle geckos get quite large, easily over 50 grams.

Average room temps are fine for gargoyle geckos. You can provide a basking spot for them if you want (some gargs will use it unlike cresties) but make sure it's a low wattage bulb. A 15w aquarium incandescent bulb would likely be more than enough.

Cheers.