Questing Druid
{1}{G}Creature — Human Druid
Whenever you cast a spell that's white, blue, black, or red, put a +1/+1 counter on this creature.

Creature — Human Druid // Instant — Adventure
Creature — Human Druid
Whenever you cast a spell that's white, blue, black, or red, put a +1/+1 counter on this creature.
Instant — Adventure
Exile the top two cards of your library. Until your next end step, you may play those cards.
This triggers when the spell is cast, before it resolves. Even if the spell is countered, the cast trigger still resolves. Copies of spells are not cast, so they won't trigger this.