Have you thought about replacing Helm of Kaldra with Chariot of Victory? In this deck it's, the only difference is that 1 less for the equip cost.

Try Alexi's Cloak. It is like diplomatic immunity, but also acts as a counterspell.

I second Open the Armory

Perhaps we could compare notes? I've been slowly trying to make my bruna deck more competitive in multiplayer EDH, but lack some expensive staples yet. Maybe it could give you additional ideas? Bruna.Win.

I like this deck a lot. I'm building a similar one but with Zur The Enchanted as the commander and Bruna as the main focus. Having that little bit of black can really make her annoying.