Well, the first thing I'd do is stop blaming man for his virtues. Greed, selfishness... these things are what the world desperately needs right now, not selflessness and an orgy of self-sacrifice.

I'd establish a totally capitalistic society based on the gold standard. I'd abolish all forms of control on the people except for the one obvious one: the right to one's rights, i.e. I would make illegal that which is a destruction of rights. (Murder, for example, because it is an individual taking away another's right to life.) I would, after settling in my own country of freedom, throw open my borders and allow free immigration to all.

No war needed in a self-sustained society.