How does silverquill work with instants and sorceries with an additional cost of sacrificing | tcgmode

I’m upgrading my silverquill deck and I wasn’t really sure if I needed to sacrifice three creatures in order to copy altars reap with casualty.( 1st sac to pay the additional cost, 2nd for casualty and then 3rd for paying additional cost again) I’m just not sure how causality works with additiona...