You said..."Im kind of confused about the D3 and how it works/does"...a chameleon can produce D3 from exposure to UVB light. It can also be given some D3 from supplements, but D3 from supplements can build up in the system and lead to problems. As long as the chameleon can move in and out of the UVB it shouldn't be able to overdose on D3 produced from exposure to it. The UVB should not pass through glass or plastic.
here are some articles that will help explain supplements to you...
http://web.archive.org/web/20060502...rnals.com/vet/index.php?show=5.Vitamin.A.html
http://web.archive.org/web/20060421.../index.php?show=6.Vitamin.D3.and.Calcium.html
http://chameleonnews.com/?page=article&id=102
You said..."dusting the crickets with clacium I have to do everytime before I feed them to my cham?"...many of the feeder insects have a poor ratio of calcium to phosphorus so dusting with a phos.-free calcium powder at most feedings helps to make up for this.
You said...."they dusted all 150 of the ones I bought at Petsmart for free"...but the powder falls off, so by the time you feed him the next time there will be very little or none left on the insects.
You said.."I feed the crickets some sort of calcium gel that substitutes for water"..I don't use that stuff, so someone else will have to comment about it.
You said..."As for the fruit, do i feed this to my chameleon or my crickets?"...I feed my crickets a wide variety of greens (dandelions, kale, collards, endive, escarole, mustard greens, etc.) and veggies (carrots, squash, sweet potato, sweet red pepper, celery leaves, etc.). Since your chameleon is a veiled, it can be offered any of the greens and veggies mentioned as well as a bit of fruit (apple, pear, melon, berries, etc.).
As for other insects, you can feed him superworms, crickets, roaches, phoenix worms, butter worms and once in a while waxworms (fatty)....as well as captive raised hornworms (NOT FED ON TOMATO PLANTS).
Appropriate temperatures will aid in digestion.
Here are some other good sites...
http://adcham.com/
http://www.uvguide.co.uk/
http://raisingkittytheveiledchameleon.blogspot.com/