Stephen

Well you're never really safe but basically some walls to get between you and the zombies. Half the time a creeper will blow out half your house anyway.

Basic progression is something along these lines;

Chop down trees and collect some wood
Use wood to make planks
Use planks to make crafting table
Use crafting table to make tools
Use tools to collect more resources
Use pick axe to mine ore and gems
Use furnace to melt ore
Use metals for stronger tools
Use metal tools to collect diamonds
Use diamonds to make Nether Reactor Core
Use reactor core and a heap of gold to make Nether Reactor
Use Nether Reactor to spawn zombie pig men and a bunch of other stuff


In the full version (I mean the PC version not the paid mobile version) there are a lot more varied terrains and other realms you can access eventually but I haven't progressed that far yet.