Well, I am of course biased in this question, seeing how I breed panther chameleons

. But before you purchase any chameleon, be sure to read up on the proper care needed and the cost in order to get the proper equipment, cost of feeding, as well as occasional veterinary care that may be needed. A site that I recommend that seems to have some really good information about the care, health, cost, and equipment that is required is The Chameleon's Dish at
http://www.chameleonsdish.com/. There are many other good sites for information as well.
For your first chameleon, I highly recommend you get a captive bred chameleon from a reputable breeder. The smaller breeders tend to take more care and attention to their breeding colonies, babies, and health. Veiled Chameleons have a tendency to be aggressive - but, I am sure many veiled chameleon owners can give you advice in this, however, this is the generally known concensus about veiled chameleons.
Panther chameleons tend to be the most hardy of all chameleons, and I have only had a few I have had to work with in order to gain trust from them. Most are all gentle chameleons. However, they are one of the most expensive chameleons to purchase... especially if you obtain one from a private reputable breeder.
I am sure many others on this forum can give more information about the other chameleons available and what type of temperment they have as well as their hardiness in captive survival.
Welcome to the chameleon world! They are wonderful creatures.
If I can be further help, I'd be happy to answer any questions. You can reach me at my site email address listed below.
Good Luck!