Oghams are not the easiest things to learn, not if you want to do it properly.
There are plenty of books, decks and sets readily available that will give you meanings for each ogham that are mostly just associations and interpretations linked to trees that draw from worldwide history and folklore. So if you were looking for a short cut to a quick and simple ogham set of meanings and association that could be one way to go, if your happy to accept one of many wide variety of opinions and speculations about the ogham.
However oghams are not all just trees and being an ancient Irish text, I see no relevance for history and folklore that is not directly related to Ireland. Trying to discern the meanings of these oghams is no simple task. I have spent the past few months working my way through the ogham and I have only just gotten past the first aicme. Not that I believe I know all there is to know on these first five oghams, but it is enough for me to begin to understand their meanings and associations, or at least my personal interpretations of these.
For most of my information on oghams I have been relying on the Auraicept na n-Éces: The Scholars’ Primer, being the texts of
the Ogham tract from the Book of Ballymote and the Yellow book of Lecan,
and the text of the Trefhocul from the Book of Leinster. There is an online version of this book found HERE. Because I can not read Irish, I have been going through the English chapters to uncover all I can about the ogham. This has been a bit of a trek as this book is not the easiest of reads.
As I mentioned above oghams are not all just trees, but reading through The Primer, the first chapter of the Auraicept na n-Éces: The Scholars’ Primer, it does associate each ogham with a tree, so it is easy to see where the confusion about the oghams being a tree oracle might have came from. However in the later chapter Ogham it describes other more varied meanings from the kennings as well as lists a number of other associations linked to the ogham, such as birds, colours, rivers and art.
In trying to decipher each ogham I have primarily used the Bríatharogam, translated as "word ogham", which are the kennings or short meanings given to each ogham found in the Auraicept na n-Éces: The Scholars’ Primer. There are three kennings for each of the original twenty oghams and these along with the meaning for the individual name of each ogham has led me to my own personal understanding of what each ogham represents and means.
According to the Auraicept na n-Éces: The Scholars’ Primer it is Ogma we have to thank for the invention of the ogham, "a man well skilled in speech and in poetry." A man who is not a man but an Irish deity of the Tuatha Dé Danann, a god of eloquence and learning, that is a reminder to me that we never stop learning. So no matter how much we think we may know about a subject there is always more to discover and no matter how much I think I may understand, or grow to understand, the ogham, where will always be more to learn. Something for me to keep in mind as I make my way through this ancient language.