Greatest Gil-making class? Fastest way to level one?

[Xystic]

I'm in it for the money, obviously.

I was thinking about Alchemy, or Goldsmithing. I am slowly working on a Mining class so I thought I might provide my own items.

I would actually check your market boards first. Observe what sells and what doesn't sell. Using that information, select the profession in demand. A goldsmith can make a lot of gil on a server where goldsmiths are lacking but on servers where goldsmiths are abundant, you won't make very much.