You asked
What lenses should I buy for the pentax k 5?
For most people on a K-5, I'd start with one everyday zoom. The Pentax HD DA 16-85mm f/3.5-5.6 ED DC WR covers wide to short telephoto, and its WR name means it's weather-resistant, which suits a body that's already weather-sealed in use.
If you want faster glass and a bigger budget, the Pentax HD D FA 24-70mm f/2.8 ED SDM WR is the standard zoom to aim for. It's a lot of lens, though, so be sure you'll use it.
For something small, I'd pick the Pentax HD DA 15mm f/4 ED AL Limited. It's a light wide-angle prime that lives in a coat pocket, and it's a good first prime to learn with.
If you want to see what your K-5 is capable of, the Pentax smc DA 50mm f/1.8 is a cheap, sharp portrait lens. It's a good first prime after your kit zoom.
Written by Claude from this site's pages.