depends on your taste and on your budget (mostly) at typically you could cover most of the range with only 2 decent zooms (maybe add a third for very wide angle)
A cheaper kit:
Pentax DAL 18-55 + Pentax DA 50-200
Mid range:
Sigma 17-70 (C) + Pentax HD DA 55-300
or
Tamron 17-50 + Tamron 70-200 f/2.8
More expensive:
Pentax DA* 16-50 + Pentax DA* 50-135 (or Pentax DA* 60-250)
Sigma 18-35 f/1.8 + Sigma 24-70 f/2.8 + Sigma 70-200 f/2.8
And add a Sigma 10-20, or a Tamron 10-24, or a Pentax 12-24 or a Sigma 12-24 to the list if you want another very wide zoom
You can always mix and match to your liking. Check the lens reviews also, it is very useful. Mostly it'll depend on your budget, cheap zooms are ... well cheap to buy (<$400 each). Good zooms are very expensive (~$1000 to ~$1700 each)
You can always go with older AF glass to save a few bucks or try your luck with MF ones, but good ones are gonna be expensive.
I'm slowly working on getting HQ zooms, one at a time, starting with a wide to normal zoom since that's what I use most.
You can also go a long way if you go with 3 good primes (i.e. 24/50/100) which would cover the same range, you would only need to zoom with your feet