- The best armor will always be Exotic. All exotic gear has the same statistical value, just distributed across the stats in various ways. As long as you're in Exotics, you're good. The exception to this are your accessories, which can be Ascended quality. Ascended armor will be added in the near (?) future, but that's a longer term goal and not something you must have right away. Weapons go up to Ascended now as well, but again, that's a goal, not something you MUST have. Honestly, you could probably get by just fine in most content in Rares and no one would be the wiser.
- You can tell what distribution of stats an item has by the name; for example, "Berserker" will always mean Power is the main stat, with Precision and Critical Damage as the minor stats. You can see all of them here;
http://wiki.guildwars2.com/wiki/Item_nomenclature
- People figured out what the Mystic Forge can do via experimentation, data mining, or ArenaNet just updated the wiki themselves. I don't know if this is still true, but I believe a few months ago one of the developers said there were still undiscovered recipes for the forge. As for it being random and useless, they don't call it the Mystic Toilet for nothing.
- They various options for different gear doesn't really matter; those are just alternative ways to get the same stats (i.e. Soldier's gear from Ascalon Catacombs tokens is statistically identical to Soldiers gear bought with Karma at the Temple of Balthazar). You just have different options. See more here:
http://wiki.guildwars2.com/wiki/Equipment_acquisition_by_stats