Cheaper Upgrading Guide by Odilbert of Scania: How to Brute Force RNG (Random Number Generator).
Instead of buying pricey CSS (Clean Slate Scroll) which currently sells for 19m in Scania and similar prices in most other worlds, you can easily upgrade for a much lower fee.
Step 1: Buy the same exact item costing around 50m or less until you have a full inventory of them. This only works for armor as the lowest spell trace is 30% which gives you high enough chance of success to be profitable, and spell trace fever increases this.
Step 2: Upgrade every single armor one single time, and no more until most, or in a perfectly mathematical world 30% (45% fever) are +1. Then take the +1’s and upgrade all of them to +2, some will fail, some will pass. Take the +3’s and upgrade all of them one single time until some are +4, and some fail. Keep doing this until +7.
Step 3: You would need too many armors, and since golden hammers are expensive, now is the time to use 100% hammers, followed by CSS 10% for the last two upgrades.
Additionally, you could have upgraded the first +1 failures for a possibility of up to +6 total.
Step 4: Take all your failures and price them accordingly in the Auction House. +4 and up will sell for a lot, +3 and up for less than clean.
Step 5: Take your +7, or +9 items if you used golden hammers, and use cheap 70% (Rare) potential scrolls on them… You now have Rare Potential.
Use 50/100% Epic potential scrolls obtained from any different events (there are plenty) or the legion shop. They take very little time to get… You now have Epic Potential.
Go to the maze/labyrinth where Gollux Prequest is, navigate it on every channel and mine the ore veins. You can get up to 4 Master Craftsman Cubes per channel from that maze alone if you explore, jumping around every room until you have found an ore vein. Note: Level 1 mining provides more cubes and less gems from veins so keep it at level 1 while you do this even if you need to unlearn and relearn mining. It will take you 20 Master Craftsman Cubes if you are very unlucky but… You now have Unique Potential.
For Legendary potential I can’t help you out as Master Craftman cubes have unique limit now. It will take a lot of money to do it… but hey Unique is pretty good for the low cost of a few million for obtaining rare potential.
The reason this works is that by buying equipment, you get 7 upgrades (at the current price of Fafnir armor 50m.) With CSS 10%, you get 1 upgrade slot at 10% chance. Usually more than 10 in a row fail but for the sake of estimating lets say one out of ten passes. Thats 190m for 1 slot. (7 slots come out to 1.330 billion meso)
Think of it as buying upgrade slots instead of buying armor.
For the sake of efficiency this will be calculated at spell trace fever time which changes 30% to 45%, which I will round to 50% because of your Diligence (Personality Stat) bonus.
It is even more profitable and makes sense to do this on armors which cost even less than one CSS, such as the Ranmaru set, which is 5m per piece, but also works for Fafnir set.
The spell traces used per upgrade on armors at the lowest % selection are 290, for an extra of 3.48 m meso, a low price compared to buying tons and tons of CSS.
Good luck and godspeed.