For me personally, I took it on my 16th dive but, didn't use it till my 17th dive.
First, I have a Sea Life Micro 2.0 with a Sea Dragon 1500 light. One of the reasons I didn't take a camera before then is that I was a little intimidated by the size of the whole setup with the camera, light, and light bar. My instructor was with us on this dive trip because several of us were working on Adventure dives for AOW and this particular dive was our deep dive. I wasn't planning on taking my camera but, my instructor suggested taking just the camera without the light or light bar (i.e. crawl before you walk). So, I stuck just my camera in my BCD pocket and off we go.
Turns out when we got down on the wreck, I couldn't get my camera out of my BCD pocket. I had on reef gloves and couldn't feel the pulls on the BCD zipper. And, I didn't want to take the glove off for fear I'd lose it. Anyway, I finally figured it out on our next dive (another wreck), was able to actually get the camera out of my BCD pocket, was able to snap a few pictures, and then stick it back in my BCD pocket. So, for me it was dive #17.
The point of my blathering is that you don't have to make the camera the focus of your entire dive. If the camera by itself is small enough to fit in a BCD pocket, take it with you. You don't necessarily have to use it. But, if you get down there and feel like it, pull it out of your pocket, snap a few pictures, put it away, and then enjoy the rest of your dive. You don't have to jump into with both feet all at once. I can honestly say that for me, it's been much easier starting out with baby steps and working my way up to the full photo rig.
Hope this helps.