Activate quick spells during the battle phase (i.e. Mystical Space Typhoon) to increase the ATK of this monster and win the battle (the quick spell itself does not need to have an ATK increasing effect). During your own battle step you can also reveal a Pitch-Black Power Stone and shift one of its counters to this monster to increase its ATK. This srategy can be used as well after summoning this card during battle phase with Magician's Circle. After the battle phase use the gained counters to activate the effect of this card.
A good strategy with this card would be to have both this and "Gearfried the Iron Knight" on the field, with "Butterfly Dagger - Elma" in your hand. When you play "Butterfly Dagger - Elma" and equip it to "Gearfried the Iron Knight", it will simultaneously destroy "Butterfly Dagger - Elma" and put a Spell Counter on "Magical Marionette". "Butterfly Dagger - Elma" then returns to your hand and you can repeat this, using "Magical Marionette"'s effect to destroy your opponents monsters and make this card's attack high enough to defeat your opponent with a single attack. "Royal Decree" or a similar card might help this strategy as well, to prevent the destruction of your monsters after wiping out your opponent's.