It will depend on several things, but the best advise is to know who you are buying your cham from!! how long have they been breeding, what is their reputation, etc.
It pays to do your homework when it come to choosing a cham to buy.
Most newbies start with a male veiled because they are way more affordable then a panther, and males are easier to care for.
You also need to take into consideration if the cham is captive bred or wild caught.
If wild, you need to know how honest the breeder is about it's health and if it has already been checked for parasites.