Go to the inn at Honor Hold (Not sure where in Thrallmar for Horde) in Hellfire Peninsula.  There is a trainer and vendor that will get you enough to get to 325, when you start getting recipes from reputation vendors with the various factions.

If you don't have the Burning Crusade expansion, there isn't much need to go beyond 300.  I don't think there are any socket items available without the expansion, and almost all of the materials to get to 375 are only available in BC as well.

You can't do jewel crafting as a profession without the expansion...

When you go to Honor Hold, don't make the mistake alot of people tend to make. Pay attention when you talk to the trainer. You need to browse the trainers goods to get the low level gem designs. Most people choose training, and miss the designs completely. I've made decent gold by buying the designs and listing them on the AH because of people making this mistake. Not sure if it's the same way for the Horde.