The easiest way to obtain this achievement is to rank up to level 30 first as more rare gear drops the higher level you are. This is because at low level Purple and Gold items dont drop at all in fact you cannot get purple until Around Rank 16* (and even then it is very rare)
*If you want to rank up quickly complete all the main story missions as they give the most XP after that do the the "side missions" .--------------------------------------------------------------------------------------------------------------------------
Once you reach rank 30 you can get Superior (Purple) or High-end (Yellow) items from either the Dark Zone or daily missions.This video will show you how to do daily missions but just keep in mind that you need a Superior (Purple) or High-end (Yellow) item in all slots (Except MODS)
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The items you need include--- Primary Gun ---
--- Secondary Gun ---
--- Sidearm Gun ---
--- Knee-pads ---
--- Pack ---
--- Gloves ---
--- Holster ---
--- Vest ----
--- Mask ----
--- Knee Pads ---
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* On one final note the April update for the game is said to include Item Trading which will presumably make this achievement far easier to get if you are still having trouble (this Update will be free)
Hope this helped everyone out and good luck!
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Daily and Challenge Missions in Depth