This effect can't reduce the mana in that cost to less than one mana
Instead of picking up a Deck Builders Toolkit, Id suggest you buy bulk of basic lands you like off of a third-party marketplace, and then bulk sets of cards from individual sellers
Those three stallers, together with Supporters like Sabrina and Blue, can buy you some time as you protect your Squirtle/Wartortle or feed your Blastoise ex with two more Water Energies to maximize its Hydro Bazooka move
Balamb Garden, SeeD Academy / Balamb Garden, Airborne Balamb Garden, SeeD Academy puts an interesting spin on creature lands, as it only requires a mana investment once before it becomes Balamb Garden, Airborne at the cost of losing the land
"Precombat main phase" refers to your first main phase
Good luck to everyone duking it out down there, and may a red deck win!