Mulligans
General Mulligans
16 of the 40 cards in your deck are basically a big spell. Your odds of drawing at least 1 big spell are almost 50% with every draw excluding the mulligan, the most important cards after that would be cards that discount your big spells. With the exception of Balinda, Mailbox Dancer and Naga Sand Witch can get you closer to the card that you need to play to win the game.
Balinda is self-explanatory.
Aggro Mulligans
P.S Other than the general mulligan cards