Know that there is a difference between a dedicated macro lens and one that has a macro function. The latter is almost a deception by the manufacturers as they rarely do 1:1 Macro. Only dedicated macro lenses usually can do 1:1. If it is a zoom lens, it is not a true macro lens - but rather it has a mediocre macro function.
True macro lenses are always prime (non zoom) lenses, and since they are specialty lenses usually have a good resale, so I would not expect to find one used for a good deal.
The inexpensive macro lenses that start out at around $300 (like the Tokina 35mm macro), are usually under 60mm, which may be OK, but you have to be very close to get the 1:1 magnification. The traditional macro lens is a 105mm lens, but on a cropped camera, you can get away with a 60mm lens.
Perhaps the best inexpensive macro lens in the 105mm range is the Tokina 100mm f/2.8 macro, which is about $450. This is the lens I have, and it is a great lens; very sharp.
Usually I don't recommend add-on filters. But there may be one exception - the Canon 500D macro lens/filter. Not to be confused with the 500D camera (what idjit would use the same model for a camera and a filter?).
Check out this tutorial by Bryan Peterson:
http://www.adorama.com/alc/article/Macro-Filter-Adorama-TV
However, I am at this point still a bit skeptical about whether or not this lens/filter is all that great. I have not tried it so I cannot say if it works well or not. But I cannot make that decision for you.
If your budget is $200 and you want macro, buy a good set of extension tubes - the ones that have electrical contacts in them (not all do). They go between your camera and lens and turn your lens into a macro lens. They are not quite as flexible as a true macro, but they give decent results and allow you to see how you like to shoot macro on a budget.
The cheap extension tubes - those that are $20 or so lack the ability for the camera to control the lens and set the aperture. While you can get those to work, they are so much hassle you will be spending time in trying to figure out how to set the camera up that you won't have time to take a good photo. So at least buy the $200 set of extension tubes.
http://www.althephoto.com