You Really might want to consider an inexpensive zoom to get started. I often see surprisingly decent autofocus zooms sell on eBay for less than $10 U.S. currency, especially those in the 28-80 range.
Come to think of it, I know a guy in the marketplace who has a 28-80 for sale that he might just give you a good deal on.
seriously though, I like the Sigma 28-80 f3.5-5.6. They are usually under $20, sharp, contrasty, and focus really quick. The downsides? They are cheaply built, are kind of slow aperture wise, and the lens hood is a terrible design. Also, the front element rotates, which is an issue for some.
Whatever you do, avoid the pentax FAJ 28-80. It is a total garbage lens. It may be the worst autofocus 28-80 ever made.