It's better to buy a set as you will see in the video. You can focus closer but get shallower DOF and lose infinity focus.
Best to use tripod and live view.Also auxilary lighting ( small LED panel ) to give pop to subjects. As your lens is 30mm which is 45mm equivalent
it will focus close so adding extension tube means lens will be closer to subject and if for insects it might be to close (scare them away)
even if you get higher magnification.
