Are you required to pay all mandatory additional costs for Wild Evocation?
If Anthony can pay the cost, and it isn't a mana cost, and it doesn't involve cards with a specific quality in a hidden zone, it must be paid if able. If it is a mana cost and there is enough mana in his mana pool to pay it it must be paid, otherwise he has the option to activate mana abilities to pay for. If the cost involves cards with a specific quality in a hidden zone Anthony may choose to pay for it if he wants to, but is not required to. If the cards mandatory additional costs can't be paid, or he chooses not to pay an additional mana cost the card is uncast and stays in his hand. 


  117.8c. If an effect instructs a player to cast a spell “if able,” and that spell has a mandatory additional cost that includes actions involving cards with a stated quality in a hidden zone, the player isn’t required to cast that spell, even if those cards are present in that zone.     


From the Gatherer Rulings:


  If casting the revealed card involves paying a mandatory additional cost (such as the one Fling has), the player casting that card must pay that cost if able. If he or she can't, the card remains uncast in his or her hand. If the mandatory additional cost includes a mana payment, the situation is more complex. If the player has enough mana in his or her mana pool to pay the cost, that player must do so. If the player can't possibly pay the cost, the card remains uncast in his or her hand. However, if the player has the means to produce enough mana to pay the cost, then he or she has a choice: The player may cast the card, produce mana, and pay the cost. Or the player may choose to activate no mana abilities, thus making the card impossible to cast because the additional mana can't be paid.