Also a note about the Earth AI3 grinding deck: It is far more economical to START with the time element. if you sold all the card of the time starter, buying the entire earth AI3 deck costs you a net 37 electrum. (also remember that quests give you ~100+ gold once you beat AI0,1,2, + buy/sell a card).
Perhaps that could be a second option for those who already have started as time mark.