First thing is that you probably actually learn more by reading here and playing the game then watching any of the lets players, but you can still learn much from them.
If you want to learn from the lets plays you should crticise what they are doing and try to make it better yourself, for example you can download the map Maddijin is playing right now, wach the game and play it yourself tring to do even better because if you can do better then the player who have the disadvantage of having to discover the map you show that you are able to improve your game.
However one thing you should never do is to take anything for the truth. I do not have any build orders, do not sort anything by tiers, for me nothing is predermitade or true.
I haven't played much civ at all but I can probably be considered as good as anyone else here and I can beat diety without problem other then I have the weakness of getting bored very quickly.