Most recommend precious metals but for most of us that means buying from some website tha most of has no idea about, credentially speaking. I fear all that is a rip off. If I could go someplace and physically purchase silver coins, preferably, where I can physically walk out of the place with them in hand would be best but I have no idea about such a place.
You can buy online safely and reliably. Just know the spot metal on the commodities exchange for that day, and price compare the online sellers. And buy it to receive it, not hold it at some remote entity. There is no advantage to buying coins, imo. You are paying for the minting process. A one ounce silver dollar costs more than one ounce bullion simply because fo the printing. Who cares! Buy 1 ounce bullion, or plates of grams for gold for example, that can be broken off for trading, buying products, etc.