I keep one male in each. But I wouldn't think twice about putting 2-3 females in with each of them.
Some day I'll probably have enough females to do that. I've found that if you give them room, they'll use it.
My 4'x2'x16" tank has another lone male in it, and he's always exploring. Every night I go in the room to check on him he's sneaking around in a different spot 
much better than when he was in the 33 gallon aquarium 
I don't really like the '10 gallon rule' because it is floor space you need to worry about.
You could have a tank that is 12x12 inches, and 15 feet tall, it would be huge volume wise, but you couldn't even keep one leo in it.
Kind of an extreme example, but you can tell what I'm getting at lol
hereare a couple of pics of the 2x4 if you're interested


-----

The following sentence is true.
The above sentence is false.
4.4 Leopard Geckos
1.0 Marbled Gecko
1.1 Red Eared Sliders
0.2 Siamese Mice