You need to rent these cards to get the power before the end of the season. Prices go way up at the end of the season (for renting). Or you can combine multiple epic cards or maybe snag an Alpha or Beta card for even more power but usually those are more expensive. Just have to keep and eye on the rental market if you want the best deals.
RE: my quest on finding the lowest gold foil legendary to rent ..Any suggestion on where or how can i rent low price gold foil that can give me 75k power.