Prior to Brilliant Stars, Build & Battle Boxes included a 23-card "evolution pack" instead of a 40-card preconstructed deck
You can use that excess mana to sift through your deck until you find a win condition
When players say this, they mean that there's no difference between winning the game at 20 life and winning the game at 1 life
Obviously paying 7 means it will be hard for you to get your mana back when you cast it that way, but the fact is, having the Adventure side means the Familiar actually stays useful in the extremely late game, something that wouldnt be true otherwise One green mana to search up a basic land is a borderline playable, especially if youre playing more than two colors
Dominaria United Jumpstart Boosters contain 20 Magic cards (including all the lands you need to play)
Take Takeno's Cavalry, a 1/1 for 4 mana that can tap to shoot an attacking or blocking Spirit for a mighty one damage while swinging for one itself (unless its blocked, and then you get a 2/2 for our 4 mana investment)