I've been thinking a lot about this topic:
https://devxf2.piratekings.online/forum/threads/refining-gem-supply.1778/
In general, as everyone saw, decreasing refining gem's supply wasn't favorable idea, as it was already too low. So I had to try to think of different approach, and something very wild had striked me, it made perfect sense to me so let me tell you about it.
PKO has strong economy, you have very huge gap between the gems and refining and unique gems, and because of that it's actually making most of people's experience unpleasantly. What we need is more better choices for players, a strong notion was to boost the regular gems, which is one of leading idea, but here's another approach: we saw some of additions of new gems had created new kinds of economy and possibilities of builds. By introducing Broken, Cracked, Chipped gems, which are essentially a unique gems with +2, +3, and +4 stat points bonuses, similar to unique gems which give +5. The exception is that those all gems are essentially same gem-type, meaning you can only forge one of quality into your equipment.
They would be also scattered in the world of PKO, allowing healthy and constructive means for players to obtain the gems, broken becoming the most cheapest and placed in lower level dungeon and low-reward lottery, and so on. With cracked and eventually chipped gems being placed accordingly, all share similar chance rates but ultimately what content's intend level that determines quality of gem. This way, you have whole segment of PKO, from the beginning to ending, you are always getting some gem, and you can choose which quality to forge. Or sell it.
I think that this is very fair approach, it most certainly promotes and encourages new comers to gem without costing them millions, and most importantly it gives refining gem the attention it's always had deserved from day one at PKO.
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