If you ike to shoot outdoor and want an all-around lens, there are a few choices:
- Pentax DA18-135mm WR,
- Pentax DA18-250mm (and Tamron 18-250mm)
- Sigma 18-250mm OS HSM.
Each lens is an all-around lens. No lens swapping. The first one is an obvious choice with the K-5 WR body, but the DA18-250mm has a solid record of outdoor usage without issue.
I shoot outdoor primarily and this type of all-around lens is my favorite. 80% of my shots are done with the DA18-250mm. The absence of lens swapping is a blessing when the weather is foul: rain, dusty, muddy.
If you want more than one lens, you may consider a combination of zoom lenses and prime lenses. A prime lens has a single focal lens. It tends to have a higher image quality (IQ) than a zoom lens because the latter needs to compromise over the focal length range.
Pentax has a very nice offer of prime lenses, compared to other brands and you may consider these once you become more familiar with your camera.
Hope that the comments will help...