Hello:
Actually, you have several options,all good.
First, what I have is the Tokina 100 mm macro lens. It cost about $475, and performs beautifully. Canon, Tamron and Sigma also make great macro lenses. Vivitar imported a macro lens at one time, and may still. Lower price, not the quality of the others, but probably entirely satisfactory.
Next, is the 2-element close-up lenses manufactured by Canon or Nikon. They are well-corrected, are expen$ive, but don't cost nearly as much as a dedicated macro lens. I think Canon's designation is the 50D lens. It comes in some strange and wonderful diameters, so a step-up ring may be necessary. Nikon makes 52 and 62 mm 2 element lenses, and it doesn't hurt a bit to use them on a Canon lens!
Next, the 3 or 4 filter diopter sets. As shown by Emu 124's excellent photos, they can do a marvelous job, and cost somewhat less. Stick with a known manufacturer, tho...they will probably be much bettEr built. IMO, $30-50 is not too much to pay for a good quality set. Avoid the "$18 Specials"...you will not be satisfied. Keep them clean!
The next option is extension tubes. These fit between the lens and the camera body, and may or may not allow autofocusing or metering, which is a shame. Kenko iis the only manufacturer I can think of that makes extension tubes that are truly autofocus and metering. There may be others, but do your research carefully, especially on eBay. Extension tubes require exposure adjustment , which is why I think it is necessary to get the ones that will allow full metering.
There is a learning curve to macro. Use a tripod any time you can. With any of the choices, your depth of field (the area in acceptable focus) will be small. Less than 1/2 inch, in many cases. Use a smaller f/stop...F/8, 11, or 16. Even then, the subject's body plane should be at right angles to the lens axis, and if you need more light think shoe-mounted electronic flash. What I do is mount my flash on the camera, then use a bounce diffuser or card. I tilt the flash about 45 degrees from horizontal. That way, the light is bounced closer to the lens' front element, and illuminates the subject very well, without the lens shadow that can be caused by the on-board flash.
I know this is a lot, but in addition, go to your local library, and check out a good book on close-up photography. It will help immensely. Good Luck! Photography is a magical pastime. Learn the mechanics, then avoid endless, useless discussions,and enjoy the magic!