Ask yourself about your photographic goals: Where do I want to go? What will take me there? How much do I want to spend? To save money and to learn photography, look at inexpensive fine old manual-focus prime lenses. The Pentax K- and M- and A-series lenses, and the Takumars (simple adapter required), are almost all wonderful, and many can still be found at a much lower cost than new autofocus lenses. Or if your budget is large, look at the Pentax Limited lenses, some of the finest optics ever made. Your desires, and how much money you have, will help determine your lens-buying. Please ask questions here about individual lenses; we are happy to help. Good luck!