to anyone, playing this game for the 1st time: dont do it. don't spill your kreds, even for 9 buyings. its a waste: you are buying cards that will merely make 1 upgrade! the game is totally w2p, and the price us high!
what's the use of upgrading troops when the enemy upgrades as well!! i play the same lvl and constantly end up in ~30 sec, no matter what i buy((((((((
In the mine, once you clear a square you can unlock deeper mining depths for more stone per square. There's also additional milestones for mining that improves the amount of resource drops that occur in there. -Ray
alexi82, the crafting system will be improved in one of the upcoming updates