if the budget allows it, the fuji 80mm macro is unbeatable and often second hand under 1k€
with the remaining budget you could/should get a dedicated macro flash
the cheapest option would be an extension tube (or set)
mid way is the fuji 60mm, which can go to 1:1 with an extension tube
getting one of the macro lenses or an extension tube with electrical contacts would allow you to use the focus stacking feature in the camera, as opposed to going for an adapted/manual lens
lighting, however, is important in macro, so a decent front mounted flash is needed (even LED does a decent job)
