Can you gust on a move trigger?

Yes, you can use Gust in response to a move-related triggered ability.

According to RiftJudge FAQ #6968, while you cannot react directly to the action of a unit moving, you can react to a triggered ability that occurs as a result of that movement (such as "When I move to a battlefield...").

Key Principles

1. Reaction Timing: Movement itself is instantaneous and cannot be reacted to (Rule 441.3.c). However, if that movement triggers an ability, that ability is placed on the chain, creating a Closed State. During this state, you may play [Reaction] spells like Gust.
2. Trigger Independence: If you use Gust to remove the unit that triggered the ability from the board, the triggered ability remains on the chain and will still attempt to resolve (see RiftJudge FAQ #11094).
3. Information Check: As per Rule 359.3.f.3, the ability "notes" information about the location at the time the trigger condition was met. Even if the unit is returned to your hand before the trigger resolves, the ability can still successfully execute its instruction (such as moving another unit) at that original location.

Typical Sequence

1. Move: A unit moves to a battlefield, satisfying its "When I move..." condition.
2. Chain Starts: The ability is placed on the chain as a pending item.
3. Reaction: You play Gust (a [Reaction] spell) targeting the unit that moved.
4. Chain Resolution (LIFO):
   • Gust resolves: The unit is returned to the hand.
   • Movement Trigger resolves: The ability still attempts to execute its effect at the location where the unit arrived, referencing the "noted" location from the trigger condition.

Disclaimer: This is my interpretation based on the rules for triggered abilities and the chain. No single official FAQ covers every possible move trigger, but the provided interaction with "Irresistible Faefolk" (FAQ #11094) serves as the standard ruling for this behavior.