Creatures like Isshin, Two Heavens as One, Krenko, Tin Street Kingpin, or Karlach, Fury of Avernus can enter the battlefield and attack right away
These decks are often composed of cheap creatures and burn or pump spells to push damage
Risen Executioner Sarcomancy Dregscape Zombie Gnawing Zombie Stromgald Crusader Festering Mummy Liliana's Mastery Skullclamp (+Bloodghast) Geralf's Messengers Grave Defiler Graveborn Muse Nantuko Husk Dark Ritual Liliana's Reaver Vindictive Lich Custodi Lich Noxious Ghoul + Patriarch's Bidding + Zombie Infestation and other potential discard outlets/tutors
You take two Jumpstart Boosters, shuffle them together, and you have an instant deck to play against other Jumpstart decks
Counters on the team each combat is a nice way to spend that mana too
This is because Elminster's -3 ability allows you to exile the top card of your library, creating a number of 1/1 flying Faerie Dragon tokens equal to the exiled card's mana value