This is to get as much electrum as possible, not intended to win against actual opponents.
More than 80% of bronze opponents have 1 HP. This will not change, even if you defeat all the decks with 1 HP, it just replaces them with another deck below them, also with 1 HP.
10 Emerald Pillars
As many Druidic Staffs as possible.
6 Horned Frogs
As many Heals as necessary to make 30 cards (preferably upgraded)
0~3 Adrenaline Rush (if you want a chance to win against normal decks)
0~3 Cockatrice (For a more normal deck)
You get ~120 electrum per win, and it takes about 20 seconds per game (including the slot machine).
Always let the slot machine run, you can get cards and if the first two rolls are the same you get 5 electrum.
For the third spin, if the first two don't match exit immediately. Don't do this if you have the bonus rare spin.
Surrender when opponent has more than 5 HP, unless you're on the fifth roll, and really want a chance at a rare.
Always rate so you only lose 15 electrum on a surrender.
Your goal is to get elemental master as frequently as possible. This means if you have to wait 1 turn for a heal+kill, wait one turn. If you have to wait 2 or 3 turns, just kill them.
Druidic Staff is the keystone that makes the real farming happen, the heal happens BEFORE you attack, allowing you to defeat all the decks with turn 0/1 plays (and there are a lot of them) with elemental master if you have more than 95 health.
It is of the utmost importance you surrender as quickly as possible against opponents you can't defeat immediately, if you want optimal electrum farming.