crested geckos are not social you can place two females together and have it work but often times it doesn't so its not really reccomended.  Not really sure about the other geckos though.

I disagree. 

cresties can and do form harems of 4-5 females easily, especially if you introduce them properly and give TONS of space. you can't anticipate a bully, though, so you have to be prepared for one girl that lives always alone, lol.

I think the day geckos are typically more territorial, but then my experience is fairly limited. 

no matter which species you pick, it's also all about the individual animal

Female leos can live together perfectly fine if given enough space and introduced right (a hide or 2 for each gecko) but it depends on the female and larger girls can/will bully the smaller ones. A 40gal breeder can house 4 females comfortably, A 30gal 3leos and so on

Julie of Black Ink Reptiles keeps her female cresties together in 2s and 3s and they usually do very well (again, except for the occasional bully)

I've talked to more people that say housing trios of Crested females together generally works well, (personality dependant), & some have said that even #'s work best (2 or 4).

I had two young female Cresties together for a bit, but separated them once they hit the "bug crazy" phase, just to be safe. I'll re-introduce them when they're a bit bigger.

Our cresties live together in groups. We have two adult females together, and a trio of yearlings (1.2). They do very well this way, but as was mentioned, you have to have the space to do it right. Don't try to cram two adults into a 10 gallon!

I've seen a male to several females work just fine. just make sure you have something for the boy when you wanna give the girlies a rest.

If you want a display enclosure you're going to want a diurnal species.
(Unless you don't mind then why not just have plants?)

I'm pretty fond of the Peacock Day Geckos and the little Electric Blue Geckos.

(phelsuma quadriocellata and lygodactylus willamsi)

As far as the giant day geckos, they get a tail issue from hanging upside down on 90* vertical surfices for too long. The tail flops over and kinks eventually becoming a permant asset.
If you are set on them do some research to find out what causes and prevents this "tail-flop".