How many characters can you level to 50 through quests?

[Niwashi]

I'd suggest levelling up your first level 50 class only doing the main storyline, class quests and sub quests from the region/area of your starting city.

You also want to pick up any sidequests that unlock features of the game. For instance, there's a level 15 quest (Color Your World) in Western Thanalan that unlocks the ability to dye armour, a level 30 quest (My Feisty Little Chocobo) in the South Shroud that unlocks the ability to have your chocobo fight with you, etc. The problem is that the game interface itself doesn't highlight these quests to indicate they're any more significant than other sidequests.

(At least it doesn't highlight them as special when they're available. It does actually highlight them when they aren't available. Most regular sidequests just don't show up at all until you're at the right level and have progressed enough in the main story to unlock them. Significant ones will show up with a red unavailable quest icon before you can do them. But then once they're unlocked, they get the same icon as any other normal sidequest. So finding the important quests is a matter of remembering where those red unavailable quest icons used to be.)