Mulligans
General Mulligans
Basically, you want to draw into you bigger spells and have something to do with your early turns.
I would throw back any Valets if you do not have secrets or ways to bring them into hand via
Do not play a counterspell into a coin and waste it the counterspell. Use Counterspell to defend your creatures from removal to keep pushing damage every round.
DO NOT play Potion of Poly and an Explosive Runes at the same time. They will activate on the same creature and be an utter waste. Trading 2 for 1 is very bad play for the deck.
My current Secret Mage list.
Basically the Spellbreaker and Pyro are for the Warlock matchup. Trying to Silence the Voidlord to get lethal through. Pyroblast helps to seal the last 10 damage before the life gain and wall of Voidlords wins them the game turn 11+.
Also if you are going to downvote the deck please explain in the comments why. At least test the deck before blowing it off as well. It has gotten me to Rank 8 with ease and I am a casual player of only a few games a day, and some days no games.