FTK lines:
2 ways to do it after resolving reasoning/monster gate
1. You need minimum 8 of the level 12 machine monsters in GY and Machina Overdrive in GY: summon Ruinforce and make Gustav max > use Gustav effect> summon 2 more ruinforce and another Gustav> Gustav effect > link those gustav away(might need to summon another Ruinforce or Machina Fortress)>2 more Ruinforce and another Gustav> link away gustav again>activate Overdrive shuffling back 3 gustav>make the final gustav
2.(if you do not have overdrive in GY but do have enough level 12 machines) Exact same process but you need 1 free card in hand. All you need to do somewhere in the middle of the combo is use Knightmare Unicorn to shuffle 1 of your Gustav's back into the extra.