I started out as Alchemist/herbalist, but after reaching lvl 70 i dropped herbalism and became a JC. I gotta say, it cost me about 1500g to get my JC ability up to the point where i could really start making back some of the money. But to be honest i still make the most money transmuting Earthstorm or skyfire diamonds, then crafting them into cut gems. They both still sell really well before cutting them, (about 30g profit per earthstorm transmute and 15g profit per skyfire transmute on my server) but i can cut them and make an additional 10-20g depending on the market in AH. The two professions compliment each other well, but you wont see any realized profit till you get both professions in the 300's.
The key to switching to JC, is first buy one stack of each type of ore that is prospectable, then prospect it just to get a feel for what types of simple gems drop. I did this and was able to save about 500g in mats by reselling unused mats that i recieved from prospecting in the AH. Side note, JCing is very expensive, the high lvl designs that you cant get from rep typically sell for several hundred per, but if you are smart and patient about it you can make that up on the back end. Pay attention to prices on AH and dont buy anything unless you are getting a bargain price for it.