I think that for someone's first chameleon, they are far better off getting a healthy baby than attempting to nurse an ill cham back to health.
Rehabilitation of ill or malnourished pets is best left to the more experienced.
After all, if you don't know what is "normal" then how can you recognize decline or improvement? Not easy, for sure.
That doesn't mean that newcomers cannot do it but it is a far less stressful and much more pleasant introduction to chameleon ownership when you start off with a healthy pet.
If you're getting a cham from an experienced, reliable breeder who sells chams that are well-established, you'll be off to a good start.
Please be sure to vary his diet and match cage and care conditions as close to the ideals as possible.
Chameleons have a very limited tolerance for conditions, watering and feeding not being perfect.
People have often been given incorrect care instructions from retailers and other "experts", so looking over the forum caresheets and asking questions is the safer option.
Here are forum caresheets with more details on the requirements for different types of chams:
https://www.chameleonforums.com/care/caresheets/
I hope you recognize that people here would like nothing more than for your new cham to live a long healthy life with you, so I hope you will stick around.
Best of luck with the new cham
