Grind to exalted with a the other playable race of your choice that has the mount you want and buy those. Rep is pretty easy to come by these days.
If your level 80 (which I am doubting by the sound of it) do the argent crusade dailys and take the scrolls of rep you can get. Otherwise
Do the starting area of the race
Find any low level towns dedicated to that race (WoW head can search for quest that give reps to certain factions, its helpful)
Do the cloth hand ins (60 wool, silk, mageweave, runecloth)