If you're having a hard time reading this I'll "translate" it to make it a bit clearer, cause this is extremely useful info (no knock against the guy above me, in fact we all really appreciate this info, so many thanks):
This is what I have for you if you have questions about upgrading these weapons. The Safi weapons have 5 slots to fill, and there are the normal slot upgrades like Attack Up and Element Up, which there can be multiple of at once on the weapon. Then there are unique slot upgrades, like a monster Essence or Reload Assist. Each unique upgrade falls under a specific category, and there can only ever be one unique upgrade from each category. Tier VI upgrades (rainbow colored) have their own category, so only one Tier VI upgrade can be present (Slots IV also falls under this despite technically not being a VI). The monster Essence upgrades only count as one point toward any given set bonus, for example: Odogaron Essence needs 3 armor pieces to activate Protective Polish. The Odogaron Essence upgrade on the weapon contributes 1 point, so only 2 pieces of the armor are needed to activate Protecive Polish. See the Skills page to find what you need to get a certain set bonus. IMPORTANT NOTE: the wiki doesn't tell how the game prioritizes which upgrades will be replaced the higher stored potential is. The game prioritizes the lowest tier skills to be replaced with skills of a higher tier, which means it's harder to find what you're looking for if you fill your slots with high tier upgrades, for example: 3 slots of Element Up V, 1 slot of Element Up VI, and 1 slot of Element Up IV. Element Up IV is your lowest tier slot. This means that if you store potential, it will try to give you a skill of a higher tier than that Tier IV slot. But if the Essence upgrade you want is considered tier II, it wil be super hard to get that perk because of this prioritization. It will keep looking for your lowest tier slot to fill with a higher tier upgrade. It does kind of makes sense in the long run because it's called 'upgrading' equipment. It's kinda dumb that there are no stats on the wiki telling you the Essence upgrades' internal tier levels. If you are new to this and don't know the tiers of the sets, I advise you to keep at least 1 slot filled with a tier I or II upgrade you can get the set bonuses much more easily. Otherwise you will end up like someone with 96x stored potential and still rolling for that tier II upgrade. So to prevent wasting your time and your mats, absolutely keep one low tier slot until you figure out the tier of your Essence upgrade. Vote up the comment above if this helped you so others can see and understand the system. If something is still a bit confusing to you, reply and OP or someone else will try to help you. Stay safe out there hunter.