Gandalf, Returned is good in that you don't need worry about drawing
Shadowfax, GotM to go with him, but I wouldn't expect you to urgently need
Shadowfax, GotM every game and your deck is small so card draw shouldn't be a big problem. Returned also works well with
Garrison of Osgiliath and
Ring of Barahir, which you could do instead if you wanted to change the deck's focus a bit.
Wise Guide is a good solution for dealing with various surprises from your opponent, such as
Saruman's Power,
Red Wrath or other nasty events.
I suggested
Shadowfax, GotM because it provides the most efficient burden removal of those 3 options, but each have their own pros and cons.
Narya is an artifact so it's harder for an opponent to get rid of, but it removes burdens slowly and adds twilight.
Foe-Hammer removes burdens for free, but only if Gandalf can fight and win skirmishes, which depends on what your opponent is up to.