I will attempt to answer your question as best I can at this moment.
Metaphysics is, of course, a branch of philosophy and philosophy is comprised of writings and teaching of philosophers who are individual people. Therefore the subject matter of philosophy, dependent as it is upon the work of individuals throughout history, can tend to be unruly at times. Also philosophy is well known for its deep complexities so that is yet another reason.
It is sometimes helpful, I find, to make the effort to group philosophers into certain categories. This is what good text books should try to do. It's easy enough to group followers of a certain great individual such as Plato, whose followers are of course known as Platonists. All Platonists have as their starting point the philosophy of Plato as set out in his well known writings and teaching. It is also possible to group philosophers by the subject matter that they tend to focus on as individual philosophers: i.e. "German Idealism" etc.
I would suggest as you approach the text books on metaphysics that you try to construct groups of ideas that you find are related to one another and try to build upward from there. You should also keep an eye out for historical groups of texts since texts from the same time period tend to be similar and therefore simpler to place in an overall context.
Also, I might suggest that you first find and read a variety of encyclopedia articles on 'Metaphysics'. Encyclopedias give you the broadest possible outline of any given subject.
Here I will give you a link to an encyclopedia Britannica entry on "Metapysics" :Metaphysics - LoveToKnow 1911
This entry, although dated, is probably one of the best overall outlines of Metaphysics around.
I hope that my suggestions will be useful to you.