I dont agree on the amumu item builds at all. Amumu was my main character since beta and you list the items in order of what you want to get first but what items you get are situational, its the same with any tank plus i would never buy a warmogs on an amumu as its not a tanking item and doesnt provide any other bonuses for an amumu.
I do like some of your jungling tactics for him although i agree with monty, going for the enemy lizard is an unnecessary risk at level 4, and if you do get ganked it will put you behind by alot.