It sounds like sharpness and resolution will be your main concerns -- unlike a sports or event photographer who's most concerned about stopping action and shooting spontaneously and fast. First, get a couple of really great lenses, the first should be a 50mm macro. Two, buy a great tripod and learn how to use it (they're cumbersome) because it will give you rock steady photos. Three, buy a full frame camera because you will need to be closer to rather than farther from your subject. You may be able to find a Nikon D3 used at a good price. The D800 will stand you in good stead for the next ten or fifteen years.