I can give you my current grid for Thunder:
4 Guardian Guns (Assault/Vigor/Ascension)
1 Mammon Gun (Assualt/Vigor/Defender)
Phantom Gun
2 Marduk Hammers (Assault/Defender/Exceed)
1 Union Lance (Assault/Exceed)
I can give you the expected grid for Dark:
3 Berith Guns (Assault/Defender/Exceed) or 2 Berith Guns and Labyrinth Axe (Assault/Exceed)
2 Guardian Guns (Pride/Defender/Assault)
Phantom Gun
3 DSvarog Axes (Assault/Defender/Vigor)
But honestly, it's just the two Berith guns that would be the critical weapons for a Dark Grid for a new player. You might be able to get by without them till next year when they run the Demons again... If you get lucky with a Samael Hammer you could use that also, but I wouldn't brick it. I'd brick the Berith Gun.
But here's the other thing about the grid in a damage cut team... it's not a huge contributing factor until you hit META. At that point, you only want/need the best and you'd only be bricking/getting weapons with Vigor or Vigor/Ascension on them.
Dejnov.