I would not use gems to buy shield. Not worth it. Why do it anyway. You can get a free shield by putting TH outside. and even if they attack you for real, how much can they loot? and they wont be able to attack you anymore for 12-16 hours. You can esily replace the amount they loot from you with 1 max 2 good raids anyway.
If you want/have gems to use, you can finish upgrade jobs. this way you can expedite your upgrading progress plus spend your resources faster so there is nothing to loot from you anyway.



