Camera body (probably want a FF body with lots of MP) If you are doing this professionally, really should have at least two bodies.... (or you may need film instead of digital.. depends on what you are doing)
Macro lens, bellows, extension tubes, etc.. unless you are talking microphotography.. whole different story.
Lighting equipment (ringlights, diffusers, etc)
possibly brackets, tripods, focusing rails, software / hardware for focus stacking (if needed) depending on what you are shooting.
rough guess without more information.... $5,0000 to $10,000 minimum to get started .. go on from there...
The other thing is.. that this is not something where you just buy a camera and some gear and jump into it... takes a while to learn to use a lot of that equipment..... especially with the precision that you would need for that type of shooting...