How to combat Thopter-Gifts with elves

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I'm planning on playing Spider elves at Grand Prix Oakland, my current board is:

2 Thorn Of Amethyst
1 Loaming Shaman
2 Viridian Shaman
4 Blood Moon
4 Umezawa's Jitte
2 Primal Command

My current board plan is
-2 Weird Harvest
-1 Regal Force
-2 Boreal Druid

+2 Thorn of Amthyst
+2 Viridian Shaman
+1 Primal Command

Thopter gifts seems to be killing me like 70-80% of the time. please help