You can be a typical Golgari self-mill deck, which is how the archetype was designed, but Golgari's card pool lends itself to splashing quite easily
The problem with Threshold is that the artwork really only communicated half of the change: for example, Mystic Zealot is already flying in its artwork
Littens Fake Out has a damage of 10, so its opponent will take a damage of 10 to its HP
That said, some modern sets like Hidden Fates, Shining Fates, or Celebrations are also in high demand
Alternatively, if you are interested in which Celebrations cards are gaining value, view the trending cards guide
Meanwhile, in most situations, the opponent will be casting whatever they didnt discard and building a lead on board which youll then need to respond to, taking the pressure back off their hand