A one light portrait can be good even though it may be simple. Like this one:

A single 430EX flash fitted with a Honl Photo 1/4″ grid. Set to manual mode, 1/4 power. Photo taken in a bright room (to our eyes. But not to the camera).  Using standard studio settings: 200 ISO, f/8, 1/125 sec).

That grid is essential. If I did not use it. the single flash would throw its light everywhere; it would reflect everywhere else’ and before you know it, you have what you did not want: the room (in this case, the hall in a church where I was giving a lecture) all lit up.

What is also essential is to have the flash off the camera (“OCF” means Off-Camera Flash). I use Pocketwizards for that, and manual flash. Some use the built-in system that your camera maker provides, usually using light pulses (not normally infrared, incidentally). Yet others use cables. Others use TTL-able systems like YongNuo transmitter/receivers. However you do it, get that flash off your camera!