Want to finally play start to finish

So I just finished Act 1, I was going to act 2 and found this new area, at least new to me that took me to conclave of the 3, just wondering if I should be doing that or finishing the normal game first? I know in the guide here it says that I need to focus on the new quests ASAP. Just wondering if I should go that route or if I should finish the normal game first.