For this achievement you need to equip High end or gold items in each slot. There is no real method to gaining these as it's all RNG but they do start dropping between lvl 25-30 from various things in game so I suggest to just do everything you possibly can. You can also craft HE gear if you aren't willing to wait. But if you plan on playing endgame content there's tons of drops through all content, I wouldn't waste the materials.
You need to equip in all these slots: