With the species you are talking about and the numbers, 1.4, I would like to see at least something 36" long. I would make sure they had a good basking light, access to quality UV, plenty of basking sites to reduce competition, and spot for egg deposition. A small water dish and the occasional misting with keep them hydrated and happy.
For just 4-6 animals I would not suggest trying to breed crickets. These guys really work crickets over when they are feeding so cricket size is usually not a big concern for adults. However, the time and effort you would have spent caring and rearing crickets could be used providing wild insects from an untreated field. The nutrient value will show up in the lizards body conditioning and colors. I have no data to back it up, but I feel I get better breeding success with my lizards when I can provide them with uncultured insects. Also, do not be afraid to try the occasional piece of fruit of veggie. Here in the midwest you can find S. undulatus often foraging around garbage cans picking at fruit. It just be an accident that they end up eating these things while trying to catch insects but don't hesitate to add to their variety.