Alright all, I'm back! I've been gone for a while, but I'm gonna update the OP a bit with some of the suggestions, including weakness policy.
Also, I've got something interesting to share with you:
Me to serebii: "Diancie's page says that it gets Trick Room at level 46 and NOT Power Gem, unlike Carbink. Howver, Diancie is not listed as being able to learn Trick Room by TM, (which Carbink can,) and has been shown using Power Gem in an official trailer. There seems to be a couple of errors here, though I'm obviously not sure."
Serebii to me: "You're right. The lack of Trick Room TM is the mistake. Fixed.
Everything else is correct."
The serebii page has been updated now to show Diancie learns Trick Room by TM; however, the level up move pool has not changed, meaning Diancie can't learn Power Gem, according to the site.
However, this official picture clearly shows it using Power Gem, meaning there is still something fishy here.
For now, since I'm more inclined to believe the official picture than serebii, I'm going to update the OP with a Specs set tentatively, but let us all be wary.
EDIT: OP now has a Specs and "Weakness Polish" set, but I'd like some help with the Policy set in determining the offensive IVs that should be used, so any suggestions would be appreciated. It has enough speed to outspeed Adamant Mega Aerodactyl after a Rock Polish currently.
Also, I've got something interesting to share with you:
Me to serebii: "Diancie's page says that it gets Trick Room at level 46 and NOT Power Gem, unlike Carbink. Howver, Diancie is not listed as being able to learn Trick Room by TM, (which Carbink can,) and has been shown using Power Gem in an official trailer. There seems to be a couple of errors here, though I'm obviously not sure."
Serebii to me: "You're right. The lack of Trick Room TM is the mistake. Fixed.
Everything else is correct."
The serebii page has been updated now to show Diancie learns Trick Room by TM; however, the level up move pool has not changed, meaning Diancie can't learn Power Gem, according to the site.

However, this official picture clearly shows it using Power Gem, meaning there is still something fishy here.
For now, since I'm more inclined to believe the official picture than serebii, I'm going to update the OP with a Specs set tentatively, but let us all be wary.
EDIT: OP now has a Specs and "Weakness Polish" set, but I'd like some help with the Policy set in determining the offensive IVs that should be used, so any suggestions would be appreciated. It has enough speed to outspeed Adamant Mega Aerodactyl after a Rock Polish currently.
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