A true macro lens (and not a lens that is merely close focusing) is optimized for high magnification.

An extension tube adds nothing to the optical path, so it's usually a better option than a teleconverter or a close-up lens that screws to the front of the lens like a filter. If you're new to macro photography, get an extension tube, because you can always use it, even if you get a dedicated macro lens later or find another solution.

A teleconverter usually isn't the best solution for macro photography optically, but it will give you more working distance, if you need it for placement of lighting.