As a lock you don't need mount money at 40 but since you have a pet to train, its still not that cheap. I was always paying more money per level than my wife's priest was. That might have changed a few patches ago, I'm not sure.
Tailoring/enchanting is a nice combination but you'll be broke most of the time.
You can't use your cloth for first aid (an excellent warlock tool!) if you are using it to raise tailoring.
You can't sell your unneeded greens in the AH if you are using the dusts for raising enchanting.
I'd recommend....
Enchanting but as a disenchanter only to gather dusts, etc... to sell in AH up until you are level 40.
and then any other gathering skill.
Unlearn that second gathering skill and go tailoring at 40 after you have your mount and 40th spells. That would mean though that you have to buy your robes of arcana instead of making your own. Its really hard to find the recipe for the robes anyway :-)
OR
Go skinning/herbalism to 40 saving/selling herbs as you see fit and then drop skinning for Alchemy at 40. My warlock was a herbalist/alchemist while leveling and it ate a decent amount of money up and you can always sell the herbs in AH for more than the potions they make with a few exceptions. If you are dedicated to herbalism and will farm herbs instead of looting what comes along (as I do) you can make a lot selling herbs and never run out of potions that are useful. Since I'm more lazy than that, I've actually bought major heals off the AH a couple of times. When all you do is instances, you aren't seeing herbs P:-) Of course, I have plenty of money by this point to where I don't worry about buying a stack or two of healing potions anymore :-)