I am hoping that once Modern competitive season ramps down some of the staples I am missing will come down in price.
Here are all the cards I am missing, or have 1, 2, or 3 of. Some I have a playset for with cards from other printings (Path to Exile and a few others). I have Path to Exile, Muldrifter, Festering Goblin, and Lightning Helix from other printings.
Here is the alphabetical list.