Ok, so durring the Harvest festival, you can buy Green Fireworks outside Ironforge or outside Orgrimmar. They cost only 20 copper and for every 36 of them you turn in at the darkmoon faire you get 8 tickets. Basically thats 7s 20c for 8 tickets. Or if you don't feel like waiting til the festival, you can buy the recipe for 18s. Although it would require 36 heavy blasting powder and 36 heavy leather.
You can either turn these in at darkmoon for rep and tickets, or you can sell them at way high prices durring the faire. I would suggest advertising to sell them actually at the faire, just yell every 30 sec or so.
Happy money making!