The four primary characteristics of money, commodity, fiat or cryptocurrency are: (1) Durability, (2) Divisibility, (3) Transportability, and (4) Noncounterfeitability. Although a number of items or assets have served as money, those that best match these four characteristics are the ones that best function as money, the ones that best operate as a medium of exchange.
The best way to buy gold and silver is to buy physical gold and silver. The best way to get it is in the following form 1) 100gram gold bar; 2) 5 - 1 oz coins (whatever is cheapest in the geolocation you are living) 3) 20-gram gold bars; 4) some 5-gram gold bars. Yes they have bigger margin over their market price but they can be easily sold back if you need to without touching your "big investment". With this setup, you never or almost never sell your 100gram bar but you can buy in or cash out everything else depending on the situation you are in. (for example gold spikes - you cash out - gold sinks you rebuy at a net profit and stack your hoard).