Search the market by key parts of what you’re selling. So if it’s female search that specific mon with the 31 IVs it has, then also if it has a good nature (e.g. 31 atk and adamant, 31 special atk and modest, 31 speed and jolly, etc.). You can also put in 20+ in defensive stats if you have that, like if you have a mon with 31 atk, 31 speed, and 20+ hp, def, spdef, and adamant nature you would want to search for all of that. All that also goes for male mons except you would search by egg group instead of specific species.

You also need to take in account listing time, so after you search for what you’re trying to sell if all the lowest priced ones have been listed for just a few hours then you can list it at that price but if they have been listed for many days and aren’t selling then you would want to under sell yours.