Quote: You have a choice between buying a system flash (meaning one that works with the camera automatically using the P-TTL protocol) or a manual flash. Both have their advantages.
There is a third possibility, which may offer the best performance for the buck.
This would be a Thyristor flash which makes its own automatic by using a built-in photocell. More than one generation of photogs did happily use these.
As an example, the Metz SCA flashes offered at about the end of analog shooting will work well with Pentax DSLRs, provided you use a suitable SCA adapter. This would be a SCA 3701 or SCA 3702.
You could get a strong flash with full automatic and also full manual for your price range.
And with these adapters, communication between flash and body works well, including 2nd curtain. If the flash has a motor zoom, this will set itself to the correct zoom position (provided you use a lens which tells the body the zoom position). Metz flashes from the MZ40 upwards will also automatically know about aperture and ISO set on the camera.
Till today, I prefer the flash automatic, p-TTL seems to get not as consistent results.
Sadly, many of the newer flashes (including Metz and Pentax) do not offer the "A" setting anymore