{eternal witness} x2, {aluren} {phyrexian Altar}, {lightning coils}
That should cover the mana costs
To make it even more potent add in a {doubling season} which not only doubles the counters on the coils but also the creatures being produced.
not seeing how you're paying for the witnesses medallion reduces it to GG, and altar can produce G but you still have a G per cycle to go before this infinite.
Had modified the combo to match workability