So, to begin with, the game is much too huge to just make an FAQ tbh. There are too many things. Anyone that's tried to make a guide has ended up making it 20-30 minutes long and they end up having missed so many things.

If someone did make an FAQ that giant, it would overwhelm the person with information and they wouldn't retain it. It is very important when answering new player questions to keep it simple, and not overwhelm them with all the little nuances and exceptions.

One of the worst things I experience in the Novice Network is if I keep an answer simple and don't mention all the little, rare exceptions, a veteran will always interject and say "but this, and that, and that..." and make the answer seem more confusing and complex than it needs to be. They will figure out the exceptions when they do it.

Part of why the Novice Network is good, or being in an FC, is you can ask what you actually want to know, rather than being overwhelmed with things you don't need to know right now.

The most common question, as you said, are things like...
  • "when do I get a mount?"
  • "why am I not gaining any exp?" (the reason is because patch quests don't give much, but new players can't distinguish between expansion quests and patch quests)
You might get better inspiration from Square Enix themselves, who make guides for sprouts themselves:It is important to stress that Square Enix does explain almost everything in Active Help popups, as well as at the end of blue unlock quests. It's just that a lot of players seem to click these off and ignore them, then ask questions as if they didn't read it.

For example, Active Help does explain what a FATE is, but you might see a new player ask about them later on...