Making money for your mount is alot easier than it seems. The amount of money you can make increases alot as you level up and the type of mobs you kill. So read this, worked great for me from lv 30 to 40. I had more than enough gold for mount, all my abilities, and fully upgrading to a new type of armor (mail for hunter) and had 50gold left over to save for a rainy day.
Rule 1) Stay away from the auction house bidding. If you spend money constantly, you will never have enough for mount. Only sell items at auction. Only wear equipment you find or make yourself. Dont buy any gear from auction.
Rule 2) if its grey item drops, take them and vendor sell them all, all of them, even if you have to drop everything and unload to a npc vendor. Those little items add up quick.
Rule 3) avoid buying unused abilities for your class. Just postpone buying the lesser used abilities. They will always be there when your on your mount.
Rule 4) pick a grinding spot you like with exp, good drops and stay there for a level or two. If you keep leapfroging you wont find anything cool to drop. So wait it out, who knows, that blue drop might just be one more kill away.