Ya if MP is your real interest SP is only useful for learning the basic game and experimenting on how to expand optimally in your first 15-20 turns. Otherwise just jump into an MP game. You'll quickly find yourself reading the entire manual
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I suppose someone could/should put out a 2-3 page "How to jump into Dom3" thread/article. That might be good for quick learners who don't want to read the entire manual but want at least a reference point on their first game.