You tagged the deck as Modern, but Chain Lightning isn't Modern legal. Might I suggest Rift Bolt instead?
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No TBR? Even as a 1 or 2-of, it is quite the finisher. I would also recommend Evolving Wilds over the guildgates since the shuffle effect will make Brainstorm much better.
No Oath of Nissa? Five colors makes me feel like the fixing would be necessary.