The best way to understand evolutionary cycles, in my opinion, is by becoming familiar with phase relationships. These are covered in Volume II. There's quite a bit of info here as well: http://schoolofevolutionaryastrology.com/forum/index.php?topic=648.0
In the most basic sense, evolutionary cycles consist of several lifetimes in which a soul works on specific theme. Rarely, if ever, does a soul get it (evolutionary lessons) right in one life time.