mtg cards like reckless fireweaver 1x Kaladesh SP/NM Reckless Fireweaver deals 1 damage to each opponent. Spireside Infiltrator - Foil -

The same goes for Cryptolith Rite which, unlike the creature and insert mentioned above, allows your creatures to generate mana of any color

It costs just over a mana per new card but affords you a good chunk of spells while digging a little deeper into your deck

Creature - Human Soldier Color tag templates(None) Lavinia, Azorius Renegade Each opponent can't cast noncreature spells with mana value greater than the number of lands that player controls

Its the ultimate insurance policy for creature-heavy strategies

And don't skip past that vigilance counter giving either, as it's much better in multiplayer than in duels