With a lot(!) of testing and refining. Also talking to some more experienced Secret Mage / Mage Players in general I came up with a Decklist, that consists of the Secret Package with the common advantages of taking board control easily, destroying win conditions with Counterspell / Potion of Polymorph and combining those with the two powerhouses of Burgly Bully together with Archmage Antonidas. I often felt that in the current Meta where Medivh lacks consistency due to a lot of weapon removals or the need the play cheap spells in order to stay in the game a swap over to Anto did the trick for me and brought this Deck from a high Tier2 to the Tier1 it deserves..
With enough attention / upvotes I am going to write a detailed Overall Strategy Guide.
Mulligans are common Secret Mage ones, such as: Lackey, Mana Wyrm and Arcanologist. Frostbolt against Classes with gamebreaking early threats (Aggro Druid for example)
Question: Why no Babbling Book?? (is by far the most common question I get when playing this Deck)
Answer: Its way worse than any other Drop you could get in your starting hand. Sure it is a One Drop that does "SOMETHING" but still there are chances you are going to get spells that you are never gonna use anyways. Sure getting a third counterspell or smth like that feels amazing but imo it is a wasted slot way better taken by Antonidas + Iceblock or some other lategame options.
Jade Druid: Make sure to not counterspell a Coin... Try to go agressive for board and rush him down before he gets huge taunters up. You lose if the Jade Ramp is too fast.
Aggro Druid: KEEP FROSTBOLT IN YOUR OPENING HAND! Try to get value out of your spellbender. Play for board and know when to go face. Most common turning point usually is Living Mana - As soon as they drop it most of the time it is a good idea to not trade, maybe drop a counterspell against their buffs. Usually you should be a in a good spot if you removed earily threats efficiently with the Pyro+Iceblock combo. If you face a lot of Aggro Druids maybe tech for a Volcanic Potion.
Hunter: Battle for board. Play smartly around Unleash + Hyena. Even matchup depending on the start of the game. Always keep in mind that turn 5+6 powerplay of Rhino + Highmane
Silence Priest: Iceblock saves your ass against the OTK. Go face whenever possible while still removing value cards like Northshire Cleric and Radiant Elemental
Quest Rogue: Only trade when you risk losing the board control. Try to fake a counterspell and maybe get a gamewinner on a vanish or even a crystal core (happened more than I want to admit..)
Taunt Warrior: Hardest matchup IMO. Prey for them not running Armorsmith. Always calculate using a face spell on a taunt minion because he might just clear the board again and you will end up with no board and lost damage to face.
Miracle Rogue: Dont overvalue counterspell. Razorpetals.. Backstabs.. Just hope for the best. Maybe they outplay themselves and play an Auctioneer into Potion of Polymorph. Capitalize on their slow starts and deal sticky damage to the face. Burgly Bully works wonders in this matchup.
Pirate Warrior: Fire War Axe is OP. If they get a buff on that you are in a bad spot. If not - Just keep and eye on a potential Frothing Berserker or Southsea Captain. Face damage is not as important as keeping board control. Try to minimize their pirate synergy as much as possible.
Mirror: Prey for the coin. Always play for board. Burgly Bully should give you the upper hand in this. Iceblock might save ur ass aswell. All in all the combo of Antonidas + Bully works very well against all types of mages.
If you have any questions don't hesitate to ask in the comments. I am constantly keeping an eye on them :) GL playing!