The Blacksmith will probably give you more than the Jeweler
Jewlecrafting is so expensive to use that it's not worth using at all unless you're combining Flawless Squares or higher, which is the point they stop dropping. The cost of combining those is 30k, so you can wait to level your jeweler until you start getting that kind of money.
In contrast, I find Blacksmithing is great for gearing out lower-level characters, or when you feel like gambling and trying to make good gear (your money is currently better-spent at the AH if you want some guarented good gear though)
Also, here's a list of what you will need to combine each gem type