Thor's 1 is great poke but not easy to get the full DPS from. Only level this skill if you are dealing with a team full of cc and can't make use of your 3
Thor's 2 is just amazing it can save your team, get an enemy killed, and over all will allow you to control who ever you want.
Thor's 3 is where a good chunk of his DPS comes from which makes leveling it is very helpful and good at turning a fight around in your favor
Thor's ult I say is what makes him one of the best junglers in the game. A fairly global ult with a stunning land can quickly turn the fight around.
Sorry not much said but I have my fair share of hours in smite. Any advice is welcomed