Cards that say you can cast a card without paying the mana cost generally look for a certain type of nonland card
There is no massive card advantage here
Commander owyn, Shieldmaiden First strike At the beginning of combat on your turn, if another Human entered the battlefield under your control this turn, create two 2/2 red Human Knight creature tokens with trample and haste
This might dip the price for a little while, but as one of the best artifacts of Commander, itll be back up above $10 before you know it
Slow means easier to interact with, and that in turn means this will probably have trouble at higher powered tables
Yawgmoth's Will lets you cast cards from your graveyard that turn, with the catch that anything heading back to the graveyard is exiled instead, but in fast formats that downside barely matters