You'll need to have 45 gold total to get your mount, 35 gold for the training and 10 gold for the mount. An easy way to make gold even when you are a lower level is by picking a gathering profession (mining, skinning, or herbalism) and selling the components you gather. Also make sure your character has as large of bags as you can cheaply get and loot everything and vendor everything you can't sell in the auction house.