people dog them but the kit lens for pentax is pretty good and useful--18-55 al II is fine, the weather sealed model probably more and kx isn't weather sealed. best part is the ability to use all older pentax glass. I prefer to stay with the A-series just because you have all functions except autofocus.
I have an A 35-105 3.5 zoom that I use a lot.
A series and below (which only do manual focus) will be very cheap compared to newer stuff. but it can be hard to focus.
Honestly, I would start with the kit lens and go from there. once you see how you use that, it will tell you what primes you might want to look at... this place has more info than you will ever need:
http://www.pentaxforums.com/lensreviews/