Rift Plat Alts is nothing new. If you've never been a MMORPG before deciding you know what I mean probably, and how easy they can do for your life.
At any banker is essentially a personality that you use the space for inventory and gain a better utilization of the auction house. If you took all three gathering professions to plate division is more than probable that the characters register and store your handset is just not enough for all the materials you collect. In this case your choice of either removing these mats on the auction or to create another character to keep it for you.
The second option is preferable because it can not be responsible for the sale. Often sold and undervalued in this case platinum waste more. Fortunately the development of a banker alt not require much work. Basically, it becomes another character and get to the capital city of your faction. After that, you can easily use the inventory to store items and relog quickly from one character to another in order to sell some items in the AH: it saves time because you do not 'do not travel with the main character.
Just like your main character, you should buy additional bags on your banker alt too. They don't need to have 16 slots immediately, but having additional space is definitely beneficial. Consider just how much space you need and purchase bags accordingly. You may also begin with several 4-slot bags you receive from quests or simply get them from the AH. They will pay off quickly.
Make sure you utilize the Rift Gold too. It can be used as temporary storage if you need it. Also, should you exhaust inventory room in your banker alt you can always make another one. It might obtain a bit difficult to keep an eye on all items across several different characters, but if you keep for example ore on a single character and herbs on another you'll get used to it soon.