Collect 6 slot bags as quickly as possible ... some will drop as loot, others can be bought from tailors ... you can do a /who and /tell and offer to buy COD (cash on delivery) via the mail system so you don’t have to buy Knight Noah from an NPC vendor or go to an Auction House before you are ready.
In fact, you need World of Warcraft gold to continue your WoW adventure no matter what class and race you are.
Have a "mule" sitting in your factions Auction House Town (eg. Iron-forge for Alliance) - create a character that is closest to the Auction House Town best a dwarf or gnome for easy access to Iron-forge - Humans need to travel via Storm-wind and the Underground tram system, Dark-Elves have to travel via foot for about 20 minutes through dangerous territory to get anywhere near Iron-forge for the first time ... place your character very near a mailbox that is not busy.
There are two mailboxes near the Auction House in Iron-forge - one is always crowded crowds = lag. Choose the one that is not busy for your log-in/log-out place. This mule you will post your stacks to for sale at the Auction House. Of course, you are able to get cheap WoW gold from the Auction House!