4 Oct 2019
Gadwick's triggered ability won't trigger when you cast it because it's not on the battlefield yet.
4 Oct 2019
Gadwick's second ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
4 Oct 2019
If Gadwick enters the battlefield without being cast, or if it was cast for a cost other than its mana cost, the value of X for its first ability is 0.