Mulligans
General Mulligans
The Mana Wyrm is a special case here, i include it because a 1 mana 1/3 is good and if you get the secrets or the Arcanologist in your starting hand it has the potential to be an effective early game tool, however it does suffer from the abundance of big spells making it difficult to get early damage instances.
Combo Mulligans
It is important to get the secrets into your hand or on the board early because the Raven Familiar and the other cards like it rely on revealing the bigger spells. Therefore an Arcanologist is the perfect card to have early because it is tempo and removes a secret from the reveal pool.
Control Mulligans
The Prince Valanar is a good choice to mulligan for against aggro classes for obvious reason, it provides curve, being the only 4 drop, and the lifesteal can slow down aggro decks enough for you to get to use the big spells.
My attempt at a big spell mage deck, the goal here is to play early game control cards or small cards that require the big spells, such as Raven Familiar , and then have enough control in the later stages of the game with the big spells to get a big enough Dragoncaller Alanna off for the win.