It will depend on what you expect from the flash. That B&H unit is a macro flash and as such, it will have a very low light output because you're shooting something right in front of the lens in macro. For fashion ring flash, you're obviously going to need something a lot more powerful.
If you are doing macro then that unit, for $80, looks like it would be worth a try!
Marco ring flashes generally have GN less than 20m.
Just realised the GH1 won't do wireless TTL with the Metz. That means any ring flash you get won't do TTL, and you will have to rely on automatic modes.