Do what thou wilt shall be the whole of the law.
As far as 'Joining' the A.'.A.'., really, there are a couple of ways.
(These are my personal opinions:-)
rretac.org Check out this link if you are looking to take the route of eventually becoming part of the A.'.A.'. that is of the C.O.T. and T.O.T.
Find a mentor (Neophyte) and take it from there.
In my personal experience, Initiations can be useful, but the true A.'.A.'. work is within ones own personal being.
May I suggest reading, if you already haven't:
Commentaries on the Holy Books and other papers, and secondly The Vision and the Voice with commentaries and other papers.
Crowley, Blavatsky et al. / Crowley, Neuberg and Desti.
Also, a great book that I recommend, and again this is my own personal opinion:-) is: The shining paths by Delores Ashcroft Nowicki.
The latter book will cover all of the path workings on the Qabalistic Tree of Life, as well as the spheres. The next step is Starting and completing the Aethyr workings.
Of course, you want to have a mentor before attempting any of this without prior knowledge.
Hope this gives some insight.
Love is the law, love under Will.
James