Get a foundation laid down with a bed to respawn when you die. You will. Often. Put a box by it with a replacement set of armour, pick, axe, torch and anything else you want back quickly when you respawn. Have a campfire or torch ready before you need it. Gets really dark really fast. And cold. Tame an easy flier, or something fast. Doesn’t need to be a good fighter, the ability to fly or run away from trouble will allow you to explore more safely. And stay out of the water for a while. Nasty stuff in the water.