The original goal of this deck was to give everyone else a ton of cards and resources, and then get yourself killed (by threat or undefended attacks) so that one fewer card appears in Staging. However, this is the Campaign mode version, which needs to survive so it can keep using these heroes.
Most important in starting hand, by far: Song of Kings. Build up, draw, and then use Protector of Lórien or Elven Jeweler to discard what you can't or don't need to play. Then Galdor of the Havens gets you six cards to keep going, and a decent draw can get you through your whole deck in one turn. Watch out for drawing unique cards that you don't have resources to play; the main thing in Turn 1 is to use up all three Legacy of Númenor. Watch out for the other players' threat while achieving this, but if Player 3 can manage one single threat reduction, you can almost certainly get it done safely.
You are carrying one essential card for another deck: Vilya. It's here in the first-player deck so that Player 3 can use it during this deck's planning phase if it's convenient. (Plus, Player 1 just draws more.) Wizard Pipe is also extremely important to the Gandalf-Vilya combo, but as it isn't quite crucial on Turn 1, there is only one copy. Narya is a nice addition, but Song of Kings for Player 3 is just fine in a pinch. Gandalf's Staff is just gravy.
This deck carries one Scroll of Isildur, mostly to repeat Mithrandir's Advice. If things are already going too smoothly, this can go to Player 4 instead. There is also one Out of the Wild to get the Keen as Lances combo started, because Player 4 doesn't draw very reliably. Good Meal usually goes to that, and to Lórien's Wealth, which can help you out of a corner if you get stuck, but is better to target someone else. The third Good Meal is ideally for Pippin, but can give you a free Mithrandir's Advice or Campfire Tales if you desperately need it. Finally, one Lembas for Erkenbrand, again because Player 4 doesn't draw healing reliably enough, and this deck is more or less guaranteed to find it.
Expert Treasure-hunter is for Gandalf, Glorfindel, and Aragorn, usually in that order. Erkenbrand is usually okay with two Cram and one Unexpected Courage, and between this deck and Player 2 there are six Cram to go around. Gandalf, Glóin, and Aragorn are usually next in line for them.