The Gods Unchained team released an update/preview of what the Daily Play and Earn system would look like once it gets rolled out, which depends on three things: Rank, Win Streak, Collection Quality. They put some charts up and an example calculation which is useful, but I wanted it to be a little more clear. I made this chart which shows what you would earn if you had a full deck of each quality and according to your rank, assuming full win streak and that you stay at the same rank. You can view these as percentages, ie. in Mythic, a purely Plain deck will earn 50% of the GODS that the maxed full Diamond deck would earn, or you can view it as GODS if we assumed the maxed player would earn 1 GOD.
There are a few assumptions I made to make this, which is that Win Streaks max out at 10 (or a modifier of 0.1), that at Mythic the modifier is 0.9 (with which I extrapolated the 8th to 11th ranks with, since we know the 9th rank modifier), and some estimation of the modifiers for ranks lower than 8 following their chart.
Some observations are that with a Diamond deck, you're earning more GODS in any rank than a full Meteorite deck at Mythic. Of course there should be less full Diamond decks than people who are in Mythic, so if you are not going to drop money to upgrade your decks, the best thing you can do (still) is to be as high ranking as possible and stay there. A full Meteorite deck actually only gives ~8% more over a full plain deck in Mythic which isn't that much.
If you instead had a win streak of 0, you’d basically have 5% less compared to an assumed max win streak. Table below for reference:
Here is a table I made assuming a rank of Mythic with win streak plus a full Meteorite deck, but swapping out some cards for higher quality. Adding 1 Shadow card will increase your GODS by 0.045%, while adding a Diamond will increase it by 1.4%. The reason why I showed adding 14 Gold cards or 3 Diamond cards is that at these levels, this will give you a better GODS earned than a full Shadow deck.
Hope this helps you better understand the system; of course they may change it before they implement it but this should give you an idea of what level you want to target for. I do have some issues with it as it stands, namely that it discourages deck variety and experimentation even during the week, but we’ll see what happens…