I don't ever use substrate with veiled chameleons...many of the
things that people use for substrate can be ingested and may
cause a blockage....so I'd rather be safe than sorry.
Most people recommend using a screen cage....but in part, it
depends on where you live. I have always used part screen and
part solid cages, but I live in a cool climate where the winters
are very dry. This would be fool-hardy if you lived in a hot
climate, of course.
Cage size for a single adult, I wouldn't go smaller than 2'high
X 2' X 18"...the bigger the better. You can house a young one in a
smaller cage to allow it to catch the insects more easily if
you free range the insects.
Young ones (up to three or four months of age) I never keep as
warm as adults...they have smaller bodies that can heat and cool
faster than adults do. They can also become dehydrated quicker
than adults. I also never house veileds together past three
months.
When veileds are about six months old they usually become
omnivores. They will eat crickets, waxworms (not too many since
they are fatty), super worms, silk worms just to name a few
insects...they will also eat leaves of plants (so be sure to
only use well-washed non-poisonous plants in their cages), leafy
greens (dandelion, collards, kale, etc.), fruits (apple, pear,
melon, berries, etc.) and veggies (red pepper, squash, slivers of
sweet potato and carrots, etc.) Some people feed them pinkie mice
but I don't. I'm not sure that they are good for them.
The cost will depend on where you live.
They are available most of the year as a rule.
You're a lucky person to be getting all those things for your
birthday!