Unless you are doing macro shooting, you don't need pTTL to get excellent shots. A large share of Canon wedding photographers depend on auto flash when not using multi-flash because auto flash tends to be far more reliable. And that's Canon which has a far-more sophisticated preflash TTL design than Pentax. (I don't bother with pTTL at all due to all the portrait reaction problems, but will use it at times on the Canon set up.) Another concern - if you are looking at really cheap third-party units claiming to be "TTL" - they likely are the old units designed for film that do not provide a preflash. The will not work properly with any Pentax dSLR made in the last seven years.
I also do not recommend settling for a strictly "manual" flash, even the ones that allow you to set power ratios. What you want is auto - short for auto-thyrister. You can tell if a flash has auto settings by looking at the front to see if it has a small hole to accept light and shut off the flash when the proper amount of light is received. Not only extremely reliable and accurate (at distances more than 3 feet), auto functions give you faster recycling and saves battery juice. I think the best of these flashes are probably on the used market (if you are looking for an old Vivitar 285hv - find one with a serial number on the front just above the tilt; newer ones are not well made or reliable due to the brand buyout about six years ago). If you can find one, the Vivitar 3700 with a universal (generic) base is very good and gives you both tilt and swivel).
Even the no-name new flashes can be OK - at least for learning - and you can find them at reputable dealers. Here's one from B&H for only $37, giving you two auto ranges up to 15 feet and 30 feet. You can use the 30-foot range with bounce and set your kit lens at f/5.6 and ISO 400. Not a lot of power, but these days you can use higher ISO without fear. It has tilt and swivel, so pretty good features for so little.
Dot Line RPS Automatic Thyrister Bounce Flash DL-82ABSZ B&H
B & H isn't entirely accurate - there is no auto range to 45 feet; but you could shoot manually to achieve the longer distances.
Good luck with learning flash shooting. Check out the Stobist blogspot for help with technique for beginner to expert levels.