Gems could probably do with a rework...

[Tired_Awaii]

To start off, gems as a mechanic I think are really nice, a way to specialize a loadout to either boost their positives or makeup for any lacking aspects is very much a nice system. However there are a couple of things about it which make the mechanic as whole kind of underdeliver. I would like to point these out and then provide some potential solutions or ideas to make the system more interesting and promote more thought into the gems the player assigns to their weapons.

For starters, the leveling system, while I can understand the idea of putting in effort to make your gems more powerful, the way that you go about it makes it shallow. Your boost in power doesn't really come from accomplishing more difficult challenges, instead its just grinding out experience. While doing harder hunts may make it easier to level them up you aren't truly overcoming a challenge in order to become stronger. 
A potential solution to this problem would be making different tiers of gems which can be obtained by completing hunts of varying difficulties. You could start off with some gems that give a little boost and as the player delves into more difficult hunts they could obtain higher quality gems which would be more rewarding than just killing a couple of enemies to max a gem out, you could even use this as an excuse to make the effects of these gems more potent than what we have currently further emphasizing builds due to the greater differences between two different types of gems of the same category.

Another problem with gems currently are the slot loadouts. The idea of having each weapon get their own unique loadout of specific gems they can use/make more use of is promising but as it stands many of the given loadouts feel lackluster where certain gem types are less utilized while others feel like they are oversaturated, and this can get in the way of build creativity. 
There are two ways i think this could be fixed, either the specific gem slots are removed or more slots are added in order to create more varied combinations of slots each weapon could have. On top of this I think making it so multiple of the same gem can't be slotted into a weapon would do some good in making the player contemplate what they use but this would probably work best with more potent effects being given to the gems. 

Lastly, one of the biggest problems with gems as a whole is their lack of variety and unique effects. Gems can feel somewhat pointless and underwhelming to use at times as the effects they provide don't really help create or push a playstyle leading to them becoming a sort of a place and forget deal as it doesn't feel as if the choice made matters. Damage gems are don't provide enough effect and are mainly overshadowed by the risky gem, support gems rely too heavily on resource bonuses, and sustain gems are bloated with gems that only negate dmg from specific hazards. 
I think currently the gems are too limited in scope, more gameplay defining gems I think would make the entire gem system a lot more worthwhile of a mechanic for the player to use. There is potential for weapon specific gems to exist as well as gems with both positive and negative effects.

Overall, while the current gem system is ok and does work, I also think it is a system that could be made into a much more impactful part of the game.