My adults eat about 5 insects every other day. It varies so much, I can't actually give a good number!
Eric is spot-on with that comment. It is impossible to provide a set-formula.
There are so many variables: what type of feeder insect is used (some contain more calories than others); the age, size and activity of the cham; the ambient temps (my chams definitely eat less during winter) and the basking temps (basking influences digestion); the level of hydration of the animal. The list goes on.
The only thing you can really do is to pay good attention to your cham. Over the time you keep the cham, you will gain a lot of experience and eventually you'll be able to tell when the cham is gaining too much weight, or losing a bit too much. Then you can adjust it's diet accordingly.
But there is no magic formula.
Kinyonga often says that she only feeds her chams as many insects as they can eat in a minute. But not even that is foolproof. In the case of a shy cham of mine, she won't eat if I'm near her cage, so I don't know how long it takes her to eat the insects. All I know is that sometimes they're all gone when I come back, sometimes there are still some left.
As humans, we don't always eat exactly the same amount of food each day. Neither do chams. Eventually you'll get a feel for it.
The same applies to supplements. There are good guidelines for those, but not even those guidelines can amount to a precise formula that should be religiously followed. The requirement for supplementation also depends on a lot of variables: the type of feeder insects used, the quality and amout of gutload delivered to the cham, the amount of exposure to natural sunlight vs UV from a bulb, etc.
Be patient, and learn from your cham.
Have a read through all the articles under the 'Nutrition' section on the
Chameleons! Online E-Zine. There are some valuable lessons there regarding how to approach cham nutrition.
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.. please, help 
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