This is mainly to give us a better idea of who to use the Event Card against this round (and in which order we want to play our duels), but it's interesting nonetheless:
Current Vault: 273
Duels: 7
Minimum cards fielded: 210
Extra cards remaining (for the Event card mainly): 63
Current Vault: 223
Duels: 6
Minimum cards fielded: 180
Extra cards remaining (for the Event card mainly): 43
Current Vault: 219
Duels: 6
Minimum cards fielded: 180
Extra cards remaining (for the Event card mainly): 39
Current Vault: 208
Duels: 5
Minimum cards fielded: 150
Extra cards remaining (for the Event card mainly): 58
Current Vault: 207
Duels: 5
Minimum cards fielded: 150
Extra cards remaining (for the Event card mainly): 57
Current Vault: 170
Duels: 4
Minimum cards fielded: 120
Extra cards remaining (for the Event card mainly): 50
Current Vault: 164
Duels: 4
Minimum cards fielded: 120
Extra cards remaining (for the Event card mainly): 44
Current Vault: 145
Duels: 4
Minimum cards fielded: 120
Extra cards remaining (for the Event card mainly): 25
The most obvious choices for early matches would be
and
since they have very low vaults (low to nonexistent element of surprise) and few cards remaining in their current vaults. Water and Earth also have very few extra cards, but I'm pretty sure they'll use the Event card against us since we're in the lead
Fire and Underworld are possibly going to benefit from this card the most since they have random cards which go in almost any deck they can field.