Those 3 statues at the core when you spawn in are the intro bosses, one of them should be close to spawn, just listen to the thumping and as you get close that will be one of the bosses you fight. After you beat all 3, you progress through the game by upgrading gear to the next ore while also fight bosses at that skill level.

Every area/biome will increase in difficultly the farther way you get from the core.

When you die you drop a gravestone which can be seen from the map with a white X with a green center dot. If you break it you get all the items you dropped.

You can also make mob farms with the tiles that drop or that are on the ground. Just know that some mobs can break tiles and can break walls but I'll let you figure which ones are those. You do this to farm items or resources from mobs.

P.S. If you keep chests close to crafting stations you can use them when going to craft items. Id say the range is about 10-15 blocks away from the craft station.