I have met quite a few people in chat which started with the deck I posted earlier, totally unupped, and I can tell you that in 3-4 weeks they already have loads of money. And I'm just wondering, how could you have "tested many decks" in only 2 weeks? 10 games each? That's DEFINITELY not testing.
loads = how much?
I spent my 1st week learning the rules, playing with friends, finding the best solutions. Then I've found the deck I listed. After a day of playing with AI3 I was able to upgrade all 7 of "the needed cards" for the Scaredgirl's deck in your link. But it was not enough to my taste. I tried playing "many" times with lots of failures for a few days then returned to AI3 grinding till I have at least half of the deck upgraded. Now after 2 weeks I have "many" cards upped, included almost all in PuppyChow's one. which gives me much better results with FG - both in speed and rewards.
I do not know how it is compared to "your people" but personally I think it was the better way to "sacrifice" more of my time with AI3 to let me start better and faster in AI5/FG.
And now my AI3 grinding would be even better as rewards for spins increased.
Well I kind of lost 10 matches in a row with that deck (4 upgrades) so I am not to sure about it, haven't got a win yet.
As I said above: FGs are not easy with many unupped cards, even with this deck. Try my way of earning coins. I think you will be more satisfied with results.