I always give them practically as much as they like when they are under 6 months old. So i make sure that their empty cups get filled. But it depends on the species and the animal you have. I bought my veiled when he was about two months old, he could eat all day...he ate about 15 or 20 crickets, curly flies and some mealworms.
But you can cut down the feeding as they grow up, to make sure they don't get overfed.
I have three chams. A 9 month old veiled, a 9 month old verrucosus and a 7 month old panther. I feed my youngest every day, a bunch of crickets. My veiled a large hopper daily and every other day some silk worms/superworms. My verrucosus every other day a variety of crickets, dubia's, hoppers, superworms and silkworms.