I bought some Red Mandolin decks that came with these and I am clueless as to what to do with them. I would only have 4 in total, so any ideas? Thanks for replying!

I would buy a deck or two of double blanks. (Penguin carries them as well as other shops) and use them for a "Blind Ambition" routine. You would use one of the decks for performance and the extra deck (as well as the 4 extra you have) just get thrown in to replace the signed cards from each performance as time goes on.

Gregory Wilson has a great routine that "I" use https://www.thesecretsource.com/l/downloads/point-blank
If you subscribe to Reel Magazine, Suzanne did (and taught) a routine on a past season of Tuesday night tricks.

It makes a much better Ambitious card routine because in reality, you are using an entire deck of gaffed cards (think of them as double backers) It gives you some really cool options with everything the exact same but the signature card.

Place card face up on deck, reverse fan deck, amaze self.
Force blank card and ask spectator not to show it to anyone but to remember the value, laugh to self.
Have fun using dealing what appears to be a four blank cards to the table (using the glide to deal the four aces).
Have card selected and returned to deck, control to top with blank card as second. Do a DL. Either turn over double and then have spectator turn over top card or do a color change.
Have card selected and returned to deck, control to second to top with blank card on top. Reveal blank card and recognize mistake, do a top change and have spectator insert what they think to be a blank card in deck in an attempt to find their card.

or

John Gustaferro's Truth in Advertising from One Degree
Get one more deck and peform John Bannon's Twilight Zone Assembly from Impossibilia
Buy 4 Blue Mandolin decks and do John Bannon's The Royal Scam from High Caliber
Roberto Giobbi's The Card in the Mirror of the Mind from Confidences (needs a Kapps Wallet)
Roberto Giobbi's Blank Card in Wallet in Secret Agenda (September 5th)

Also, Craig Petty has a great DVD with a lot of blank card effects called (appropriately) "Blank."

EDIT: I didn't realize that the cards were double blank -- just assumed they were blank faced (which are much more practical). The effects I listed are for blank face.

Craig's DVD is great and does use double blanks.

You could do Darwin Ortiz's "New Back Off" by writing down words on one face of the cards and magically printing them.