Good tips above
I started with small screws and coins on a table. Actually if they're well used, at macro 1:1 magnifications all the little nicks and marks are cool.
If I had no flash, I'd start with a slightly higher ISO around 400-800, and play with different apertures to get a feel for depth of field, and adjusting shutter speed to suit. Goes without saying this is in full Manual exposure mode, and manual focus on the lens too. Set the lens focus to whatever magnification you want, then move in and out until the subject comes into focus. Once you get a feel for what distance you need to be at mag 1:1, it will get easy. You only have to move millimetres forward or backward to get focus at around 100mm from subject. You'll see what I mean
My "go to" settings are f/11, around ISO 400, shutter speed around 1/100-1/200 depending on ambient. But I use a flash, and you may struggle with light on those settings and have to bump up the ISO and keep the shutter speed down.
First toy to get next, IMO, is a flash and some way of diffusing it. But I predict we'll talk about that later
