tap the ? At top left part for the tutorial.
If that didin't help its basically a numbers game. the larger the value it will flip the lower value side. ? Coins are randomizers it could lower the value of ur cards up to -2 and could increase it up to +2 to all sides of ur cards placed in the randomizer (use with care). As much as possible i would avoid using them unless i have a really powerful card that it wont matter if its -2. Tip is disable autosave. Play with a villager if you lost, restart. Selim and Ghart card are pretty strong early game.