Well, Elemental isn't like Civ as far as I understand.  What you do is research a path, like War, Magic, etc.  When you hit the mark on a research path, you choose a tech to get.  Some techs do lead to others is a quasi-tree, but it just opens the next tech up that you can choose the next time you fill up your research bar.  Some techs, the non green ones, have a certain chance that youll be able to select them as they dont shop up every time.  Its a crude description, I know.  But I hope it kinda makes sense.