I've been keeping and breeding leopard and fattial geckos for the past few years and can honestly say they are a blast and very, very easy to care for; just make sure you do your research. We got a crested gecko a month ago, and I think they're even easier to take care of than the leos and fattails.
Here's a short list of Pros/Cons, but I'll warn you, I'm biased in that I love them all -
Leopard Geckos -
Pros:
-Many morphs to choose from
-Reasonable prices Anywhere from $15-2500
-Pretty docile; Godzilla at birth, but turns into a puppy dog in a short period of time
-Relatively easy to care for; need heating, hides and properly gutloaded insects
-Super prolific; one female can produce 16 babies a year
Cons:
-Needs heating
-They're everywhere - if breeding/monetary gain is your goal, it'll be harder to find your niche that's not already filled, but not impossible
African Fattail Geckos
Pros:
-Super docile; only seen one aggressive one, but he was possessed by the devil
-Some beautiful morphs; amelanistics can be unnaturally bright orange
-If you're successful at producing these, you should be able to make a good profit with these; market isn't saturated
-Easy to care for; very similar to leopard geckos
Cons:
-not as prolific as leos; make sure you get Captive Bred ones, that'll make it a little easier
-still need heating
Crested Geckos
Pros:
-don't HAVE to feed any insects; new Crested Gecko Diet is touted as a replacement for feeder insects and other supplemental fruits
-very docile; mine bit me once, but it didn't hurt as much as a leo; I think their jaws aren't as strong as leos/fattails
-Prolific
-Come in all different colors/patterns that are produced seemingly at random in some cases; it's not necessary to have Super high end parents to produce high end offspring (although I'm sure it helps, they are very variable in thier offspring)
-NO SUPPLEMENTAL HEATING; ROOM TEMPERATURE IS FINE!!!!!
Cons:
-tails don't regrow (not really a Con, because they're fine without them
-difficult to find visibly sexed females and when you do, they're a bit more expensive
-can't think of any others.
I'm by no means an expert and this list isn't even close to being complete, but the above are why I would recommend any of those geckos to someone just starting out in geckos. Good luck
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Rob Jenkins
herpcam.com