Richard
The 'best' strobe is the one that best suits you. There are few limitations with your camera, as long as the flash has provision for a flash sync cord that is needed from the lens. Do you want a small 'camera top' type flash? Or a larger hammerhead type flash, with more power?
Any flash will be triggered using the sync cord. A purely manual flash ALWAYS gives the same flash output (the power is given by the 'guide number' - the higher the more powerful). Hence, either flash distance or the exposure on the camera has to be adjusted, as the flash will always flash the same. The exception are flashes with power settings, that allow 1/2, 1/4 etc power outputs. These are very useful, especially closeup.
Many (most) flashes also have one or more automatic settings. In this case, the flash 'reads' the light bouncing back from the subject and cuts off the flash duration. This is similar, but not as good as TTL, as the flash sensor does not necessarily read the same angle as the lens. (It means a shorter flash duration than manual, though, which is better for fast action stopping).
Lastly, a flash meter can be used to read the required exposure, based on a test flash, a la studio flash set ups. Metz, at least, recommend against this, saying it can be inaccurate with small flashes. I am sure it can be adapted successfully, though.
Like Tony said, I think a book is good. Most photo books will describe using manual/auto flash.
You will need some sort of shoe for a small shoe-type flash, either with a prism on the camera, the accessory shoe for the side of the camera or on a flash bracket. The hasselblad bracket is good (even the older ones), but there are others.
The Vivitar is a long standing 'small' flash choice, but there are others, eg Metz (they made the Hasselblad hammerhead flash) and Sunpak. Both make good flashes. There are fancier choices, like Normans, too, that some people are passionate about.
Nick