How often will you do macro work? If you do it quite a lot then a dedicated macro lens makes sense. Otherwise, unless you get a focal length that you'll use a lot for other things it's taking up space in your camera bag & not getting used.
Extension tubes are a viable option, but there is the light loss to contend with.
The closeup lens fmw speaks of (a dual element one) I've found to be most to my liking. It, like extension tubes, can be used on nearly any lens. It takes up much less room than a set of tubes. I use a Canon 500D (that's the dual element one, don't get just a 500) in 77mm thread. Any single element closeup up lens is IMO not worth the effort except if you only plan to shoot 3 macro shots each year.
And if that's the case you'd be better off getting a macro reversing ring for you camera or a macro coupler ring (screws two lenses together) because you'll get better results.
If you're really cheap you can always just turn your lens around and tape it to the body. Or, hold a reversed lens in front of the lens mounted on your camera. Depending on how careful you are you can get get some rather lomoesque results.
Determine desired usage/results and proceed from there.