Hmm. OP, you admit you have a lot to learn. Unfortunately you've come to the wrong place to learn it. Not because of this site's regulars' lack of knowledge but because of the shortcomings of the bulletin board as a medium of communication. You asked short apparently simple questions that want a book length answer. What you'll get here are short answers that usually miss most of what matters.
So buy a book. Two books, actually. A. A. Blaker's Field Photography is an outstanding book for beginning photographers and the ideas it presents apply to digital as well as to film. And Lester Lefkowitz' The Manual of Closeup Photography offers a deeper treatment of macro work. A couple of Blaker's formulas are incorrect, Lefkowitz gets everything right. Both are available at low prices from sellers on abebooks.com, alibris.com, amazon.com, ...
OP, you asked whether to reverse a lens or to put it on extension tubes. Which should be done depends on the magnification at which you intend to work. General purpose lenses are optimized for shooting with a large subject in front of the lens and a small image capture device behind the lens, i.e., for magnifications < 1:1. When shooting above 1:1, you'll have a small subject in front of the lens and a large image capture device behind it. In this situation the lens should be reversed to preserve its optimizations.