Deck Helper comment: This deck was posted before the 1.32 game update and as a result may work very differently now. Use at your own risk.
This deck can make up to 290 electrum (before spins) from level 5 EM.
I don't know if this deck (or one similar) has been posted, but I have found it helpful to get upgrades.
Hover over cards for details, click for permalink
58o 58o 592 594 594 594 594 594 594 5c6 5f6 5ro 5up 621 621 6qq 6qq 6qq 6qq 6qq 6qq 6qq 6qq 6qq 6qq 6qq 6qq 6u6 717 71c 74b 74b 7aj 7am 7gp 7k2 7km 7km 7km 7km 7km 7km 7q5 7q5 7q5 8ps
This may not be the fastest way to make $, or to win upgraded cards, however it is a quick way to upgrade the cards that you want. (I don't like to sell the upgraded cards that I do win).
The win % is lower than a lot of other decks, but is not as boring as many of the grinding decks I have used, and has the satisfaction of big rewards.
This deck also works without upgrades.