In my mind, and my family, "stacking" is for providing a special type of long term financial security, not for "making money".
If all goes well, we will probably never sell any of it and it will all go to our daughter, who will hopefully understand what it is for.
If we do sell some, it would only be after a major reset of its value compared to other durable assets, land in particular.
If your intent is trading, then I suggest that you trade paper derivatives, not physical.
That is what they are made for.
They have very low round-trip costs, can be done from anywhere on a smart-phone or laptop, and do not involve walking around with bags of PM or money which has some risk, as does mailing stuff.
In Thailand, round-trip on physical gold bullion is only about $7 an ounce at any local gold shop, but less than $1.50 an ounce on the Thai Futures Exchange.
As my wife is Thai, there is no tax on profits, unlike some other places.
Finally, unless you have a huge amount of money to start with, or are on the right side of a huge price reset, any profits will be very limited unless the trading involves leverage.
Gold futures on the Thai exchange have 24 to 1 leverage, so a 4% movement in the gold rice either doubles or wipes-out the margin gambled.
If you want to make smaller, safer bets when you expect a significant price movement is imminent, options or puts would be a better way to do it. They are not available here in Thailand, but are on larger exchanges.
BEFORE doing any of this, however, you should study enough that you firmly believe you understand what is going on.
Futures, for example, is a zero-sum game, and I would guess that 90% or more of people who play lose money, same as FX.
Given the leverage involved, volatility analysis and risk management are very important.