I considered Ertai Resurrected or Fangkeepers Familiar here, but as a pure counterspell Im giving the nod to Fear of Imposters
After that, you will be ready to open envelopes of cards that will allow you to build a deck full of varied skills
Charizard ex Booster Pack: Charizard Why Theyre Good: Speaking of big Fire-type bruisers that want Energy, Charizard ex is an absolute monster when fully charged, dealing a whopping 200 damage with Crimson Storm, which will one-shot every Pokmon in the game at the moment
Legality depends on the tournament format -- Duress can be legal in some formats and banned or restricted in others
Making 2/2 tokens with vigilance at a rate of one token for three mana, two tokens for four mana, three tokens for five mana, etc is honestly quite good, allowing you play both offense and defense as well as put a bunch of material in play as the game goes on
Drop some gigantic instants and sorceries in your graveyard for next to nothing, sac this, play them all at once