Then youll use your energy, always as a result of a trigger or activation, never (yet) as a casting cost in the upper right corner or a card
It is the cards themselves that hold the key, there are types of design and certain mechanisms that go a long way to minimising both mana floods and mana screws
As you can see, this format has all of the mana you need but just one spell cast per turn, so only copying one per turn won't be a restriction, and getting the copies for free each turn is big value
That said, three mana for one and a sacrifice isn't anything to scoff at
This is compartmentalization at its finest for a lands archetype
It also gives your creatures haste for , which means you can get a lot of extra damage out of your early creatures and your dragons on the turn they come in