As for starting a young individual I always recommend a critter keeper, too large of an enclosure for a young gecko will cause issue the main one, the gecko will not be able to find it's food.
For a single adult I recommend a cage that is 18" x 18" x 18" or better 18" x 18" x 24"
For a trio 36” x 18” x 18” or 36” x 18” x 24” will make a great enclosure