Thats up to your level of motivation! I think wed all enjoy reading both sides!
Implement regular and premium loot boxes! The regular can be purchased for 100 gold coins but take 24 hours to open! Premium are cash only and open instantly with the same rewards.
Least invasive: unique Mario costumes that cross over from other game properties. Money only but new skins created and added each week. No chance of duplicates, and chances fir specific skins listed.
Also include option to buy specific skin outright.