Gideon's Triumph

• WWizards of the Coast2019-05-03
  Official Ruling
  Gideon’s Triumph targets the player, not the creature or creatures to be sacrificed. A creature with hexproof may be sacrificed this way.
• WWizards of the Coast2019-05-03
  Official Ruling
  A creature that was put onto the battlefield attacking didn’t attack, so it can’t be sacrificed.
• WWizards of the Coast2019-05-03
  Official Ruling
  Controlling more than one planeswalker of the appropriate type won’t have any more of a benefit than just controlling one.
• WWizards of the Coast2019-05-03
  Official Ruling
  Whether you control an appropriate planeswalker is checked only as the spell resolves.
• WWizards of the Coast2019-05-03
  Official Ruling
  A creature that attacked and was removed from combat (such as by Spires of Orazca) still attacked, so it can be sacrificed.
• WWizards of the Coast2019-05-03
  Official Ruling
  Gideon’s Triumph can be cast after combat damage has been dealt. In this case, the target player chooses one or two creatures that attacked or blocked this turn and have survived combat damage.
• WWizards of the Coast2019-05-03
  Official Ruling
  Gideon’s Triumph can be cast before combat damage has been dealt. In this case, it can be cast before or after blockers have been chosen.

Rulings via Scryfall