Single or Multiple Characters?

[Lucke]

You get access to 2 retainers during the storyline to help with inventory. You can also buy more retainers for added sub cost each month.

[Gerolan]

Personally speaking I have five characters, as I wanted to try out all three nations,I also wanted a dedicated gatherer, and one I can simply focus on endgame with, I've always been an altaholic though

[Failia]

Of course, it's also great not leveling anything for a while and logging out in a town or somesuch each time you log for the night. I have yet to see the end of my additional +50% for rest so I get 100% on all kills.

[TheTen]

Tip: You can easily level your first class to 50 by doing nothing but the main storyline, class quests, Hunting Log and any FATEs you come across. (In the late 40s, you may have to add a few leves and extra FATEs, the game slows to a crawl around 45-50). You can safely leave all side quests untouched to come back to when you level your next class. This will make leveling your second and third class a bit easier.
Tip 2: If you know you will level all classes, don't be afraid to greed roll every pink and green (and eventually blue) gear you come across. You will use it later, and you are not taking away anything from people who need that gear right now, because Need rolls have priority over Greed rolls.

[Merryl]

This game is honestly too massive for multiple characters. You probably should stick with one.