Originally posted by Nesster Should you wish to get a prime, I suggest any of the Pentax 28mm's or 35mm's out there. They both will get you a taste of the resolution possible, and work very well indeed stopped down for that 'infinite focus zone' effect.
If you get a Super/SMC Takumar with the screw mount, you'll have to get the Pentax screw to K adaptor. But once over that hurdle, the world of low priced screw mount lenses opens up for you.
In K mount, if you can find the SMC-A version, you'll retain full exposure automation: IMHO worth it. With plain K mount, you'll have to do manual exposure setting.
With your budget, you can easily afford three to five old lenses!
Alternatives to Pentax 28's are the Vivitar 2.5/2.8 variants.
A 28mm works great for landscapes on 35mm film. The 35mm is also usable for landscapes on 35mm film, but my experience has been that it is often just a little too long. It seems to be better suited for street photography.
On digital APS-C, both the 28 and the 35 are a little too long. I sometimes use my 28mm or 35mm for landscape stuff, but the subject is usually a waterfall or mountain that is some distance away. You generally would need something 24mm or shorter. Your kit lens (as noted numerous times above) is your best option. The maximum aperture is a little on the small side, but for landscape work, a tripod and/or plenty of light is usually the norm.
When you are ready to move to a prime, the cost/value leader is still the Russian-made MC Zenitar 16/2.8. It is also one of the most compact ultra-wides out there. The dream lens is the various models of the Pentax 20/2.8 or the old Zeiss-Jena Flektogon 20/2.8.
For both your kit lens and the Zenitar, distortion may be corrected using the very affordable PTLens tool.
Steve