You should be very accurate when playing any version of this game. I’ve played both Android and Windows versions and turned out there’s not much difference between them. Before you kill the Wall of Flesh you’ll only have hellstone as a tool. You can make the molten gear with it and kill the WoF. Then you’ll have to break down altars with Pwnhammer. This will let you generate some ore (cobalt or paladium). So from this moment on, you’ll just have to break more altars to get more ore.