You asked
What lenses should I buy for the pentax k 3?
For most people, I'd start with the Pentax HD DA 16-85mm f/3.5-5.6 ED DC WR. On the Pentax K-3 it frames like 24-128mm on full frame, which covers most everyday shooting, and it's weather-sealed like the body.
Add a small prime for low light and a nicer background. The Pentax HD FA 35mm f/2 is a compact choice that frames like 52mm.
If you shoot people or events and want more reach, look at the **Pentax HD D FA* 85mm f/1.4 ED SDM AW for portraits, or the Pentax HD D FA\* 70-200mm f/2.8 ED DC AW** for sport and wildlife.
Written by Claude from this site's pages.