There’s usually not much you can do to significantly improve a smartphone macro attachment itself. The simplest option is to move closer to the subject if your phone can still focus.

A practical DIY-style option is to try a loupe as an add-on lens. Smaller loupes often provide stronger magnification and can work as a simple close-up optic in front of the phone camera.

That said, smartphone cameras normally use very wide-angle lenses, so changing them effectively with a homemade setup is difficult. Because of that, DIY solutions can be limited and may not give a big improvement in image quality or ease of use.