One fast and easy tip, dont "cash out". By cashing out you are continueing to legitimize their system. If you need to " cash out" you clearly arent keeping enough of the fiat around and should adjust accordingly. Give unto Caesar what is Caesar's. Caesar wants fiat trash for "taxes", just have enough on hand to give them when needed. To help with the fluctuations look at the 1 year SMA and buy more products and services when it is above that level (which will have downward price pressure) and buy mostly only essentials when it is below that level (creating upward pressure).
Edit: You don't need their currency to be wealthy. By no longer legitimizing their system, you are wealthy.
The DNM bible is what you're after. It's offline at the moment, but see the top pinned post in /DarknetMarketsNoobs for instructions to download the offline copy