Why did you choose Delta rather than another carrier?
I don't think it was until recently that they imposed the three gift certificate limit per ticket, and thought I could use up to $400.00 worth of $50.00 certificates for a domestic flight ticket.
Truth be told, I really just outsmarted myself. I realized going in that the T&Cs said you cannot use the airline fee credit towards the purchase of a ticket or for a gift certificate. Then I found out that I could beat the system by using the credits to obtain gc's for $50.00 or less. Well, you can, but the "work around" has its limitations!
Got no one to blame but myself!