youd buy a starter deck of cards, customise it with booster packs and then challenge your friends to duels
You could, for example, sneak in Shark Shredder, Killer Clone mid-combat if it's your commander
R Rare Accel Synchron X DARK Level 5 [ MachineSynchroTunerEffect ] ATK 500 DEF 2100 1 Tuner + 1+ non-Tuner monsters Once per turn: You can send 1 "Synchron" monster from your Deck to the GY, then activate 1 of these effects
For Fusion Monsters, the archetypal playstyle has many cards with Fusion Summoning effects including: "Odd-Eyes Fusion", "Pendulum Fusion", "Performapal Odd-Eyes Dissolver", "Performapal Splashmammoth", "Performapal Trump Girl" and "Performapal U Go Golem" for a Fusion Summon
Aunties Teahouse Scry 3
The reason Im discussing them first is that they are the smallest unit of lock-breaking an opponent can do