cast it on Turn 3, and assuming you make your fourth land drop the next turn, you can cast Astor and have that one extra mana available
Plus, in a pinch, they can be enchanted to large enemy creatures that the red-white player doesn't want to have attacking them
Once you do that, it will unlock decks to start your collection, one for each color, that you can play right out of the box
Constantly dealing instants and sorceries not only provides you with a great opportunity to buff Vivi with +1/+1 counters (and chip away at your opponents health total), but also provides you a boost to your mana pool meaning you can afford to cast even more spells
Some stores may sell certain booster boxes for less - so keep your eyes peeled for deals
Either option scales up in multiplayer