Depends completely on you, your play style and what you like. What is your other profession? Your other profession greatly determines how fast you can lvl your enchanting. Tailoring is perfect with enchanting, and you can lvl both insanely fast and cheap if you know how (check out the link to my guild's website below for guides on this).
Skinning/herbalism only make money in pure quantity of what is sold. Mining has a bigger pool of buyers and some big sell items. Enchanting is just cool esp. in upper lvls, and you do not need a gathering profession to lvl it. Also tailoring is good to feed enchanting, you don't need to gather for it and clothies can make their own gear with it. Leatherworking pretty much depends on skinning as does blasksmithing and engineering for mining.