If you are looking to get a 'starter' chameleon, I would suggest a subadult male veiled. From the experience I have with veileds and panthers, veileds seem to be a bit more forgiving.

As long as it is an healthy animal, getting from a show should not be an issue. However, I would not put it past some of the sketchy vendors to sell stuff that has not been kept properly(which could lead to issues to you). So if you know somebody honest that cares for their animals I would not hesitate buying from them.