What the achievement asks
Fully upgrade the Reshii Wraps. Ten points.
What it actually costs
The Reshii Wraps come from the K'aresh campaign. From there, each of the four upgrades costs 3 Ethereal Strands, so a full upgrade is 12 Ethereal Strands.
Strands come from the Heavy Trunk handed out at the end of a K'aresh delve, at roughly one per run. So the honest shape of this achievement is about a dozen delves. There is no faster source and nothing to buy.
The fourth upgrade is the one that matters
The last rank is called What Lies Beyond, and its effect is that you can see treasures in K'aresh while Phase Diving.
Thirteen of the twenty-seven treasures in Treasures of K'aresh are completely invisible below that rank. Not rare, not hidden: absent. Players fly to correct coordinates in Untethered Space, find nothing, and conclude their list is wrong.
So this achievement is not a side project. It is the prerequisite for the largest treasure achievement in the expansion, and the twelve delves you run for it should be treated as the first step of that one rather than as a separate errand.
It is warbound now
This was originally tied to the character, and players reported doing it once and getting no credit on a second character. It was made warbound in patch 12.0.5, so the upgrades now carry across your characters.
If you have an old half-upgraded cloak on a character you no longer play, check before you start farming: you may be further along than you think.
Where it fits
One of seven under Unraveled and Persevering, part of Worldsoul-Searching, the War Within meta. The delves you run for strands are also where the rest of the K'aresh branch gets its reputation.