Ok so I'm just making sure that I fully understand before I jump into it. Crested geckos like a taller tank, so a 20 gallon tall will work for one gecko. They need a lot of foilage to hide in. Paper towel is the best substrate. They eat mainly fruit, but also eat crickets and mealworms. They need to be misted once a day or as needed depending on humidity. Tempurature is not that important. Lighting is not a necessity
Unfortunately, it's not easy to sum up crestie care in one paragraph. There are many, many ways to safely keep and care for them!
I think a regular 20 gallon on it's side would be more appropriate. I've found, however, that front-door opening terrariums like Exo-Terra or Zoo Med 24” x 18” x 12” is an ideal habitat for a single, adult crestie. For a young gecko, smaller enclosures such as Kritter Keepers work well. Foliage and branches and hides should be provided. Cover the tank with about 50% foliage, and leave some empty space for jumping and climbing.
You're going to get a lot of people recommending a variety of substrates. Paper towel is fine, and poses less risks than a particulate substrate. However, many keepers find that a natural soil or moss is more attractive and encourages natural behaviors, as well as holds moisture. If you have a young gecko under 15 grams, I would avoid a natural setup and stick with paper towel. ANY type of substrate can be an impaction risk as can anything that can be swallowed.
As for diet, there are many people who lean towards doing it "old school" with mashed fruit and insects, but for beginners and ease of feeding, Repashy Crested Gecko Diet is great. It cuts down on risks of over and under supplementation, and provides macro and micro nutrition. You can still feed bugs twice weekly, and if you want to blend up a fruit smoothie once or twice a month, that's fine too. However, over 10 generations of crested geckos have been raised on CGD so it is a tried and true formula that takes a lot of worry out of raising cresties.
Humidity & temps don't need to be tightly controlled as with more delicate species of gecko. You'll want to have a wet and dry period, from 90% after a good nightly misting to about 45-55%. Depending on your tank, you can just spray once during a 24 hour period. Stay under 82-84 degrees as they are prone to heat stress over 85. A range from low to high 70s is ideal. You do need a day-night cycle but you do not need UVB lighting, as pointed out.
So you were pretty close but there are lots more details as to the hows & whys of crestie keeping! :biggrin: