Originally posted by Tansy ... macro lens ... on a tight budget ...
What lenses do you already have?
Consider a Raynox DCR-150 or DCR-250 for approximately $70 USD instead of a full macro lens. They attach to the front of an ordinary lens and have a good reputation. The DC-150 paired with a Pentax 55-300 can get a versatile range of magnifications by zooming.
There's a running discussion with sample photos in the PF Raynox club. The thread is 10+ years old and many of its linked photos no longer work, so maybe read the first few pages then jump to the end for recent photos.
The Raynox Macro club - PentaxForums.com
Regarding budget, extension tubes are even less expensive Raynox but introduce some complexities because your camera no longer controls the lens aperture. There are also cheaper diopters than Raynox but image quality might not be as good.
Having said all that, if you still decide to get a lens, every model of 50mm macro and 100mm macro made by Pentax gives good results, and shows up fairly often on the PF used marketplace. 50mm is better for larger subject like flowers, 100mm for small insects. (other manufacturers also made good macro lenses but are less available)