Dig deep and wide, searching for veins to mine.
DYNAMITE!
Manage your stamina, it drains slowly in the mine and faster when mining. Don't run out of stamina in the mine or you'll never get back up. Sleep to recover.
Manage your inventory, you can't take everything with you at once.
Manage your torches, you have a limited number of them and navigating in the darkness is... hard.
Ore prices reset every day, should you sell now to free up inventory or wait for better prices?
Spend your coins on torches, dynamite, upgrades for inventory, pickaxe power, max stamina, rest stamina etc.
Earn enough coins to buy your freedom.