It's recommended that you use one that has a beta carotene source of vitamin A since beta carotene (prOformed) sources will not build up in the system like prEformed sources can and this leaves it up to you to decide if/when it needs vitamin A. I've used Herptivite for years....but there are lots of ones you can use.
I think you need a source of PREformed A, as many sources believe that a chameleon is incapable of converting beta carotene into a useable form. Repashy plus is popular, but as Kinyonga stated, too much is dangerous, so use it once every other week, lightly.
You need a calcium product without D3 and Repcal, Repashy, or Sticky Tongue Farms Indoor formula are all reputable, and a calcium with D3. I like Repashy LoD given every other week.
Your schedule should be similar to:
Week 1 : Plain calcium 2-3 days a week and vitamins one day a week
Week 2 : Plain calcium 3-4 times a week and calcium with D3 on day a week
Week 3 : Repeat week 1
Week 4 : Repeat week 2
Use a good gutload, review the many threads on gutloading, but using the search feature, and if you have and adult male, reduce Calcium to 2-3 times a week, once he's an adult, but keep everything else the same. Adult females should continue to get 3 days of plain calcium per week and everything else the same.
Yes, we need to know the species you have or are researching about! I have a young veiled and use Rep-Cals calcium no D3, w/ D3 and multi-vitamin. My little guy seems to be doing great with the common schedule of Cal no D3 every feeding and using D3 every other week and multi- vitamin every other week that D3 is not being supplemented.