What range of loading are you interested in? Target, mid-range, or "lively"?
The .32 H&R Mag works with a lot of powders...
Here's a link to an article from Handloader Magazine... lots of good info
.32 H&R Magnum Pet Loads
Another great resource for loads for a great many cartridges in general, is the M.D Smith website, this is the link to the .32 H&R Mag loads:
M.D. Smith .32 H&R Magnum
I use Unique for many of the different cartridges I reload, so I also use it for .32 H&R Mag. I'm using 3.5 gr. of Unique with a 90 gr. hard cast lead SWC, out of a Ruger Blackhawk and my S&W 16-4.