Which G.D. group? There are several.
If you are looking for the Cicero's: www.hermeticgoldendawn.org
If you are looking for David Griffin's: www.golden-dawn.com
Robert Zink's: http://esotericgoldendawn.com/ourorder.htm
There are also smaller groups, such as Nick Farrell's: http://www.auroraaurea.com/en , The Open Source Order of the G.D.: http://www.osogd.org/ , or even the Magical Golden Dawn: http://magickalorder.com/index.html .
There are many groups that claim to be the G.D. Which one is right or wrong? Well, in my opinion, they all have good qualities. If you are looking to learn the basics, any of them will teach you well, although the Magical Golden Dawn does things a bit different from traditional G.D. groups and I'm not sure how I feel about them.
If you want as close to the original teachings as you are going to find, either the Cicero's or Griffin's groups are what you are looking for.
At this time, I am not involved with any of them. Too much politics and fighting amongst the leaders. But, I'm not a beginner. Any one of them can take you through the grade of Adeptus Minor. After that, you won't need my advice. :)