...I have read many care sheets and spoken to other Cham owners and found that not one person does it the same
This is because every situation is different. Different ages and genders of chameleon, different lighting or outdoor exposure, different gutloading practises, different selection of bugs, different brands of supplement.
You may find these blog entries useful:
https://www.chameleonforums.com/blogs/sandrachameleon/65-supplements.html
https://www.chameleonforums.com/blogs/sandrachameleon/174-whats-supplements-brand.html
My panther chameleons essentially do not go outside. Therefore I add D3 to their diet by LIGHTLY dusting feeders approximately twice a month, even though I do have UVB bulbs (either reptiGlo or ReptiSun 5.0, NOT passing through a screen). I use a vitamin supplement (without preformed vitamin a) once every other week maximum (generally the week opposite to using D3). I use a calcium (no phos, no D3) powder lightly dusted on most crickets. I rarely dust anything other than crickets, mealworms (which I dont offer often) sometimes superworms, and occassionally silkworms. I almost never dust stick insects, moths, roaches, butterworms, cabbage loppers, isopods, grasshoppers, etc. I pay great attention to gutloading well, and providing a wide variety of insects.
Although the above schedule has worked perfectly for me, resulting in healthy long lived chameleons, some people find they need to occassionally provide preformed vitamin A. Too much preformed A is toxic, but a little can be helpful - especially if you dont provide a good range of prey. calcium, D3 and A all work together.
As others have said, gutloading is critical. I feel a wide range of prey is also important. Suppmentation is supposed to supplement, not replace, good nutritional intake. Info on gutloading:
https://www.chameleonforums.com/blogs/sandrachameleon/75-feeder-nutrition-gutloading.html