depending on the species they need both high humidity and very good ventilation.. this is what makes them one of the more tricky animals to house in a captive environment this is the reason for using live plants and misting 3-4 times daily it helps keep humidity levels up in a well ventilated enclosure
I would suggest a veiled for a first chameleon since they are from more arid environments and seem to one of the more hardy species and can be bought from breeders very reasonably priced ($30-$60)