Check out my 60-slot backpack:
Only gold members can have more than one bag slot, free players like me are limited to the one. So when I bought that half-price Station Cash that was on sale recently, this was the second thing I bought after the mount. Very useful. I don’t know if it’s good value for money and whether bags like this show up in the game as well, but I think it was worth it.
Note that Vanguard doesn’t spam your inventory quite as heavily as other games, so you might get by without this. Not all enemies drop things, and many of the things they do drop stack. This is better than in some games, such as Runes of Magic, where you’re basically forced to buy some sort of storage expansion because of all the collectibles and runes you lug around all day.