If you are starting a new character, and don’t want to twink it with gold from your main char, getting bags is a must.
Now, bags can be expensive, especially the bigger ones, so here are some places, you can loot bags for free:
* Wharf Master at Rachet: Old Moneybag, a 6 slot bag.
* Captain Sander’s Hidden Treasure – Captain Sander’s Booty Bag (Alliance only) at Westfall.
* Digging Through the Ooze in Wetlands – 10 slot bag
* Sturdy Lunchbox 12 slot bag can sometimes be had from the drops from mobs of Venture Co. Foreman in Stranglethorne Vale.
* Swirling Vortex, Thousand Needles can occasionally drop a 12 slot bag
If you can get somebody to boost you through a dungeon, the horses in the stables at Shadowfang Keep also occasionally drop a bag (with 10 slots, if I remember correctly).