First, know what stats you are wanting first and foremost. For me and my Warlock, I wanted 100 Recovery, 100 Discipline so I simply stockpiled any armor that had good drops in those two areas. Be sure to check the ritual armors every week, as they change, and can net you a piece with some good stats on them from time to time. That means checking Drifter, Shax, Devrim, and Vuvuzela (Zavala) every week. To unlock all that armor for purchase, you need to finish weekly milestones (8 bounties in crucible, Gambit, and strikes... as well as rank up Devrim) Once you have a set from your collection built, have a look at what mods you run. Some give you bonuses, some will penalize you, so be aware of that. It takes time, a little luck, and a lot of patience to get there, so good luck!

High stat armor certainly helps, but there are a few extra things. Certain mods like “Radiant Light” or “Powerful Friends” give a bonus stat increase. Some stasis fragments do the same, “Whisper of Shards” and the like.