Well that depends on the species you'd like to work with. Either way, I suggest you get a male. They are bigger, more colourful, usually more docile (not always true!), and you don't have to worry about egg-bound females.
The two most common species are Panthers (130-200$) and Veileds (35$-100$). You also find, on occaision, Jacksons, Werners, Fischers, etc. But lets stick with Panthers and Veileds for now.
This is a male panther (smaller, tamer, more colourful but small colour palette):
And this is a male veiled (bigger, more agressive, wider colour palette and great patterns):
Of course, some chameleons look better than these, and others look worse. You'll need to look up more pictures if you haven't already chosen.
I myself went with panther chameleons. I really like them - very cool to work with. Smaller size makes them easier to house, too. Unfortunately I was cursed with aggressive chameleons, but I don't mind
If you live near me in Toronto you're welcome to come take a look. Or if you're going to the show there'll likely be lots for sale (however I don't suggest you buy this soon - you don't have a cage set up and haven't done enough research).
But tell me which you like best and then we can start on looking for caresheets and going over specific aspects of care.
Zoe