The GW2 wiki is very robust and will cover most game information you need.
Metabattle and
Snowscrows for highly optimized builds. This will only matter if you intend to do high end PUGing for fractals or challenge mode strikes, or if you are doing PvP or WvW. Otherwise, GW2 is a very easy game and you can get by with almost anything. The only "wrong" build you might land on would be trying to do open world content as a Druid, a healer designed spec with no offensive capability. For years I was following the blog of a guy going through GW2's story and content and he was constantly complaining about how long it took to kill anything as a Druid.
Lord Hizen's youtube channel also shows off very good builds, though many of them have become outdated due to rebalance patch made a couple months back.
Lastly there are the class subforums on the GW2 forums, however the activity varies. On the Ranger subforum there are only a couple guys who have been consistently posting a lot, trying out different builds and discussing their findings.