G'day Coach.
Congrats on getting the K-7 - you will find a whole new world of photographic opportunity open up for you with this little beast.
Portraiture demands a lens that has the ability to separate the subject from its background (a large aperture) - a most highly recommended lens to fit the bill is the Pentax FA 50 f/1.4. It's cheap (relatively), but very good.
As for lighting, just as with portraiture, there is quite an art and a science to making all elements come together to produce a fine portrait. I'd suggest you start with some books (like Brian Peterson's "Understanding Exposure") and online tutorials (such as on this forum) to get you started on the fundamentals.
For example start with:
https://www.pentaxforums.com/forums/photography-articles/39743-understanding-...-kit-lens.html https://www.pentaxforums.com/forums/photography-articles/62522-exposure-shutt...rture-iso.html https://www.pentaxforums.com/forums/photography-articles/49478-what-focal-length.html https://www.pentaxforums.com/forums/photography-articles/23232-learning-basic...echniques.html
Hope you enjoy your time here.