Fast lands like to get things done sooner rather than later, and they enter untapped when you control two or less other lands
And you are in the color of burn spells like Comet Storm or Jaya's Immolating Inferno or Exsanguinate effects to turn life loss into kills fast along with fast mana makers like Ritual effects in your colors
To do this, you can open up your binder and right-click
However, several factors can also influence this number, such as mana tutors, card ramp spells, cantrips, mana curve, and MDFCs (Modal Double-Faced Cards)
If we stopped there, I would have picked something else (probably Scepter of Eternal Glory)
in his GY and immediately convert recovery into damage and attack