How much is needed?
None.
How much can you take? Up to 5 if training naturally. Even up to 10 if you have a very good insulin response to move it into the muscles or are using exogenous insulin. Will excess hurt you? No you'll pee it off.
Is it hard on the kidneys? No, people are getting creatine and creatinine confused when they say this.
How often do you need it? Only after an intense workout. You don't use that much up during normal daily activities, it just gets used up if you are lifting hard and heavy.
One doc I'm friends with told me, "you'd better leave that stuff alone, it'll wipe out your kidneys.". Another one was sitting with us and said, "look at him and ignore him, look at me and listen to me, it's apparent which of us knows about bodybuilding", as we ate our chicken salads and the other guy was eating his pizza. He then shared a couple of studies with me that showed that creatine is very safe and NOT harmful to the kidneys.