Well, it is an ok size for 2 adult female leopard geckos to live in, you'd want it to be tall not long for cresteds.
Why two? Are you planning on breeding or just looking to fill the space? You could always block off part of the enclosure for one leopard gecko. I would highly suggest getting one full grown until getting another, just because there is some bit of a learning curve... at least that is the rule in our house. Gotta successfully grow one before getting another.
Check out "The leopard gecko manual" or the complete guide to rhacs for more information. Also check out the subforums here for both kinds, good luck.
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0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock