I will mirror what has already been said. Veiled and Panther are the best beginner and most common chameleon. However, veiled are a bit larger and tend to have a less pleasant disposition. This is not always the case, but in general. I have had 2 veiled and 3 panther chameleons. Both of the veileds were pretty mean and VERY territorial. One would actually lunge at my hand and bit me good more than once, I had to use thick gloves anytime I went in his cage.
I have never been bit by a panther chameleon. They will some times puff, but rarely more than that. That does not mean panthers will not bite, just that mine never have.
I think more often than not people make that first chameleon decision based on price, therefore many get a veiled as their first. I say, do your research, set everything up BEFORE getting your chameleon, and find the chameleon you REALLY want, what ever that may be.