For adult dragons, suppliment once or twice a week but lightly dusting a feeding of crickets (lightly dusting means there should be a very light coating on the crickets...the crickets should not look like they have been battered in white stuff. Just a light 'dusting' like a back table about a day after being dusted in a day (or less, depending on the amount of dust floating around in the house). A pinch of each powder is usualy all you need for a feeding of crickets or other insects.
If feeding a healthy diet with plenty of variety, you don't really need to suppliment a multivitamin more than once ever two weeks and calcium no more than once a week. A varied diet would contain at least 3 different greens (collards, dandelion, endive, for examine) several vegetables (carrot, green beans, bell peppers, zuccini etc) and a bit of fruit (strawberries, any of the melons, peaches and other non citrus fruits) and even a few edible flowers (hisbiscus, pansey etc). The type of greens, vegetables etc should also change every couple weeks or months as well. Adding a bit of Kale one week, or even romaine lettice (neither is good as a staple, but fine when combined with other calcium/nutrient rich greens such as collards etc) will give much needed variety.
Variety doesn't stop with just greens and vegetables. Offering a variety of insects is also good. Crickets, silkworms, roaches, butterworms, superworms, hornworms,grasshoppers, pill bugs, etc are all edible bugs for bearded dragons. Offering different types, gut loaded before feeding, will give your dragon beneficial variety and keep his interest too. Stay away from fire flies (lightning bugs etc) as these are toxic. ALso stay away from wild caught hornworms as these are toxic as well. (domestically raised hornworms are fed a special diet that lacks the toxins normally found in their natural food (tobacco and tomato plants) thus they are harmless. Wild caught hornworms kept and fed on the special diet will still be toxic or should be considered toxic. I don't know how long it takes fo rthe toxicity to leave the worm's bodies. Domesticated hornworms most likely were collected as moths or allowed to pupate in captivity and the eggs hatched, then fed the special diet, so toxic comonents never entered their bodies).
Also be careful in collecting wild insects that you search in areas far from any insecticide use. Some areas may seem isolated but may still be sprayed, especially near roadways where the shoulders and ditches may be sprayed to kill plantlife to prevent ditches from being over grown. Insects in these areas could have some of that poison in or on them which could prove harmful to your dragon. WIld caught insects can also contain parasites that may harm your dragon.
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PHLdyPayne