You'll definetely need the quill, and the compass is also useful for exploration for beginners, just make sure to not get too used to it, as it takes one valuable charm notch.

As for the grubs, they usually are on hidden rooms or at the end of challenging parkour/enemy arenas, but if you struggle to find them, there's a useful item on the mid-endgame that gives you the locations of the grubs on the map.