Profession TrainingFollow

Enchanting is definitely one of the best professions to go with tailoring because of the ease of leveling by way of tailoring. Alchemy and inscription require herbs, so it would be a bit on the side of money sink - however, potions are always needed. On the other hand, tailoring at higher levels does require a lot of enchanting mats, so it is still probably more beneficial. Downside is that it can be a bit grueling to level at certain points (around 275 and 350 were the most annoying parts for me, personally, but opinions differ).

Unless you are rich...

Alchemy = stupid. Where will you get the herbs?
Inscription = stupid. Ditto.

enchanting = smart. You can use it to make gold early in order to waste it buying cloth to level your tailoring.

If you are rich, forget what I said.

Enchanting is an awesome second choice, though it can leave you penniless. DEing Quest Rewards and using them to level up I still manage to stay afloat though. I'm not rich and don't have epic riding though.

The primary reason why I choose enchanting as a second Prof though is the Ring Enchants. Can only do on your own rings, so it's the only way to get them. 19 Spell Power per ring, 38 Extra Spell Power. Not much, but every little bit helps.