{T}: Add {G}. When you spend this mana to cast a Dragon creature spell, you gain 2 life.
If more than one {G} produced by a Scaled Nurturer is spent to cast a single Dragon creature spell, the delayed triggered ability associated with each mana spent will trigger. You will gain 2 life that many times.
The delayed triggered ability will trigger whether Scaled Nurturer is still on the battlefield or not.
The mana created by Scaled Nurturer can be spent on anything, not just Dragon creature spells.