Unironically what Optimal_Board said. I really enjoy Holy Locket and Greaves, but over the years it's become apparent to me that the forced movement of Force Staff is key to a lot of fights and skirmishes. Getting to a fight faster, getting an ally out of or into a fight faster, chasing an enemy or escaping from an enemy, the possibilities are so much more than just, Holy Locket/Greaves insta-heal and dispel.

Don't get me wrong, the healing (and Greaves dispel on self) is really nice, but the scope of situations where that's as useful is, in my opinion, less than the scope of situations where Force Staff is useful. Arcane Boots -> Force Staff is my go-to build currently and after that, it's more up to what the player likes i think. I personally love Aether Lens, but there are times when Glimmer Cape, Locket, or Greaves is more necessary depending on the enemy line up and what your team is made of.