At what level can you go to Magran's Teeth?

Do I need to complete faction quest first? I know you don't have to, but what I wish to ask, is it advisable to complete as many possible quest for advancement in gameplay?

What I'm supposed to do with quest surrounding Poko Kohara Ruins?

Best site for full quest order/list?

Officially, the game usually doesn't break no matter the order you go in.

 

But then the quests and stories don't always make sense.

 

I'm not sure what the best advice would be here. If it was me, I'd do a large large majority of my quests before Magrans Teeth.

I didn't beat my first playthrough and started another but I think Eotas said we can visit him when no more about current situation. So it would be better if you finish Poko Kohara quest before meeting with Eotas again. 

Otherwise from storytelling point of view it will be like: 'Have you learned the truth, Watcher?" and your characters just standing there embarrassed.