You asked
What lenses should I buy for the pentax k 70?
For an everyday kit on the K-70, I'd start with a standard zoom. The Pentax HD DA 16-85mm f/3.5-5.6 ED DC WR covers about 24-128mm equivalent and is weather-sealed, so it suits the K-70's own sealing. It's the one lens that handles most days out.
Add the Pentax smc DA 50mm f/1.8 for people and low light. It's a cheap, great lens, and on this body it behaves like a classic 75mm portrait lens. If you shoot in dim rooms, the Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary gives you a brighter zoom range.
Before you buy anything else, check the three questions and think about what you'll want in two years, because you're really buying into the Pentax K mount.
Written by Claude from this site's pages.