Most of the builds here are made by elite Crucible speed runners. That’s basically what they’re interested in so they GDStash items to mini-max their builds as much as possible.
You get gear by playing the game, farming monster totems, rogue-like dungeons, running Crucible if you have it and/or Shattered Realm if you have the Forgotten Gods expansion.
For levelling you might want to have a look at this beginner build.
It’s for a PRM build rather than AAR, but should be close enough.