Hi,
Depends on what you mean by budget. If you shop around a bit on the web, you should have no problem picking up a 105mm Sigma, 90mm Tamron, or 90mm Tokina for around £200, if not new, then in mint condition. All are true 1:1 macro lenses and deliver excellent IQ.
FWIW, I would personally stay well clear of close up lenses/filters. While they can give you good results under the rigth conditions, they are cumbersome to use (for one thing you loose focus in anything but the macro plane), and the IQ will more often than not be dissapointing. I got a not-too-cheap close-up filter early in my venture into macro photography, and it was quicky banished to the back of a cupboard.
Extension tubes are in principle very good (as good as your lens that is), but apart from losing light you again loose infinity focus. I am considering getting a set to use with my macro lens to obtain magnifications beyond life size. But I would consider them more of a specialist equipment.
My advice at the bottom line is that if you can afford one of the lenses above (or find an even better deal on a 2nd hand lens), go for it. It will allow you to get into the wonderful world of macro photography with least fuss and dissapointment.
Thomas