You can now talk to Mutamix Bubblypots in Central Thanalan (23x,13y) and trade him 5 pieces of materia. He will then give you a random materia that won't be one of the ones you gave him and of the same grade or higher.
Now you are ready to use this tool, if you have the app just look for the materia VI and V prices to update them. Then buy 5 different types of materia, the cheapest ones with positive profit numbers you can find on the list. Trade the 5 different materia to Mutamix and with enough repetitions of this you will profit(By getting more expensive materia in return).Every trade has a risk of loss, but overall(if profitable on the list) you will profit, so do this with a healthy gil account(depends on server prices).
Another risk is that prices will vary from the point you made the purchase to the point you are selling the materia. Do it at your own risk, there is an element of chance but if profitable, the odds are in your favor. If you use 5 of the cheapest materia, your profit will potentially be closer to the Improved Profit side, if you use 5 of the most expensive but profitable materia it could be even less than the Profit shown as this assumes average but still profitable prices.If any prices below have 0 it means they have not been updated in our database, we update our database through volunteers using THIS app. Any questions/comments? Join our Discord
Approximate statistical breakeven to buy any materia V at 526
Approximate statistical breakeven to buy any materia VI at 350
Approximate statistical breakeven to buy any materia VII at 225
Approximate statistical breakeven to buy any materia VIII at 129