First, are you sure you want your first sanding job done on a Dorko? That's an expensive razor to destroy.
Second, if you sand it AT ALL, then you will lose the gold leaf. Even metal polish quickly removes it.
Finally, the grit you begin with is determined by the extent of the damage/corrosion. It might be 80 grit, but it might also be 600 or higher.

I would suggest that you practice this with a crap razor. Most people don't get their first hand sanding job right, with the most common mistake being the failure to completely remove the scratch pattern of a lower grit before moving up to the next.