If that's the one that screws onto the front of the lens like a filter then I really wouldn't bother as they tend to give poor IQ and be very dark and will leave you very frustrated.
If it's a set of 4 filters with numbers 1,2,4,10 (IIRC) then these can be helpful to a point and can be had from about £15, but still wont give you anything really outstanding but will be better than the other alternative.
The best thing to use is a set of extension tubes that attach to the camera and then the lens attaches to them. They normally come in a set of three and can be used in any combination to give the desired effect. There is two types of tube sets, one type allows AF and one doesn't. The AF type are expensive (anywhere from £60 to £120 depending on make) but you can get a set from around £10 (never used this type and seem trickier to use) but both will get you impressive results.
I got some decent photos with the set of 4 filters but they just left me feeling as though I wanted more. Other than that, you could look for a dedicated macro lens but they're going to run out at £200 plus for a basic 1:1 macro lens and can go up to a canon 100mm L macro lens that I bought for around £650. If you get the macro bug it can be expensive, but it seems to get me the most gasps from the viewers.
