My flash system started off basic - one Pentax AF360FGZ plus the onboard flash. For wireless mode the onboard flash needs to fire as master, so to eliminate its shadows I use a Lumiquest diffuser and/or a section from a plastic milk bottle. In mid-October 2008 I added a Pentax AF540FGZ unit.
The EXIF data can be deceptive - most images use flash despite what the "Flash off" box says, unless exposure shows as over a second or so.