A few protips:
1. The most recent combat pots (e.g. Grade 4 Tincture of Strength) for the stats Strength, Dexterity and Intelligence always sell. And they sell pretty fast, especially if you offer them in small stacks of 10 or so. That makes the price for the small stacks around 10-50k, which people are more willing to buy than a 99 stack that costs 100-500k
2. Go for diversity. Instead of only crafting an entire 999 stack of the same pot, which you keep offering, craft all most recent pots. Also craft some buff food. And some of the highest level craftable gear. Also sell a bit of the aethersand needed in those recipes (Levinstrike Aethersand). The more different items you offer, the more stuff you’re potentially selling.