So what would you recommend to make the photo not as flat?
Mostly it's about the light. You could use a reflector or a strobe. Or take the picture in a place with better light.
The biggest benefit to my photography was learning off-camera strobes (mostly studio lighting at the time).. And I mostly shoot with available light. The benefit I got was from learning to "make the light happen" --I started paying attention to the light I was seeing when I wasn't using flash.
You can certainly improve things with post processing, too, but that just helps a little. Getting the light right helps a lot.
.













