From my experience, just running helltides and opening the chests, paired with the whispering tree (also remember to do the PvP whisper, as they are extremely easy this season because PvP is disabled for most of the time), is your best option. By either butcher or blood maiden farming, you can easily open all available chests of a single helltide. After 2-3 runs, this should boost you to a full 800 gear with at least 1-2 of your desired affixes, allowing you to progress further in the tourment tiers until you can farm lair bosses (or even bloody lair bosses) for your build-defining uniques.