How to use Vivitar 320 manual flash Off camera?

Hi! I have a Nikon d5000 with 18-55 & 55-200mm lens & a Vivitar a320 flash, my question is what would be the best inexpensive way to use this flash Off my camera, I'm mostly into portrait photography.

The least expensive way would be to use Ebay radio triggers, one on the camera and one on the flash. Also inexpensive, but more picky in use, is a simple optical trigger.

If the flash has a PC socket, you can add a mate to your camera with an adapter, and do it that way.