Macro lens is worth its weight in gold (kinda)! You can use it for other than macro shots as well, it is not just limited to the close work (although that is what it is best at).
If you can get good sharp images from your kit lens, you can crop the photo and then resize it to get a close up. You need a good original if you go this route, but you can get some good results. Usually will not compare to the results from a macro lens though.
I find teleconverters good for outdoor wildlife photos, but for detailed macro stuff you will see the degraded image quality. Extension tubes are nice, but they can be tricky to focus and also to control depth of field. I have a set that I bought off eBay for $10 that I use with some old manual focus lenses that I have.