The best food to offer is Repashy MRP (crested gecko diet); Clarke's MRP is not to bad. If your gargoyles like insects, then you could off them dusted in calcium once a week....if they don't like insects, no problem as the Rapashy MRP is a complete diet for them.
Housing multiple gargoyles is strongly not recommended as they can be very aggressive towards each others. With that said, some people (a few breeders with years of experience) have had good luck housing 2 adult females...it all depends on the temperament of the both the females. Housing babies and juvies together would result in fighting and dropped tails that do regenerate; however, the regenerated tails do not look as colorful as the original tail.