Pick up one of your signatures
If youre looking for an example, heres my $150 Teshar, Ancestors Apostle deck from earlier this year
That's seems pretty strong, and you can flash it out while their card draw is on the stack to resolve first
The Master, Multiplied, gives you exponential copies of itself as long as it stays in play and keeps attacking (and not getting chumped, I guess)
This can just sit around and make mana for you early, and then when you get to the later part of the game you can start sending it after your opponent with all your extra mana
(You are way behind if, at any point during this turn, an opponent had 10 or more life than you, controlled at least three more creatures than you, or had at least three more cards in hand than you.) To determine if you are way behind, check the game state as it was at any point during the current turn, regardless of whether Knight of Lost Causes was on the battlefield at that time