Hi Ben,
Not sure what you are after? Is your goal prepping or "investing" (I put "investing" in quotes because gold is a shiny rock. Its not going to appreciate a lot in value on its own. There is always more coming out of the ground, so people who make money in gold are "speculating" - the rise in Gold price over the last 10 years has more to do with Fiat Management and inflation than it does with the value of the shiny rock. If you think Gold may someday be "money" - in that its commonly taken directly in trade as currency, then it has potential to gain "buying power" , otherwise, it much more like sticking money in a mattress, as a hedge against hard times, than it is a growth vehicle. Many people have done historical ratio comparisons with Oil or other commodities to decide if its under or over valued at a given moment- the implicit assumption being that a set amount of gold should be able to buy a particular set of goods regardless of what year it is or what fiat prices are attached to them.) Investors take advantage of periodic changes in market conditions to make money. Buy and Hold is not a good strategy if you are looking for real gains. Of course in a mark where treasury bonds are sold at negative real interest holding on to what you put in, is a gain. Gold should track inflation fairly well.
Silver is similar but more prone to market variation. 90% of silver demand is industrial - so even in a collapse, you may see prices fall as businesses are no longer buying it for use in their products. Gold has almost no commercial demand, and is therefore the better inflation-tracker.
There are many different forms of PM "investing" - Mining Stocks, ETF, Certificate accounts ( bank holds your gold physically for you), "stacking" (in possession holding) etc.
The paper market is certain suspect if not outright corrupt. Many allegations are floating around about naked shorts by large players to manipulate the prices. (in other words, its not much different than the HFT controlled stock market at this point) - "paper" gold has significant counter-party risk, and really just isn't a good idea at this point ( I don't think) - Take physical delivery and then loose it in a boating accident.
There are also counterfeit bullion products out there- so you need to make sure you buy from a reputable dealer (though last year we found out that won't always protect you- its entirely possible at this point that fakes being MANUFACTURED by respected mints) - and probably prefer many items in small quantity by different manufacturers instead of say one large gold brick - thus minimizing the risk that all of your stuff will turn out to be fake. There are chemical and electrical tests that can be done on bullion to determine is authenticity - but they test surfaces- you have to file into or cut a bar to be sure. Then you get to reforge it because no one will buy it back in that condition. Also many bars come in ASSAY packs - blister packs with a certificate - stating the history of the bar. Again, it helps, but its not a guarantee- especially if the manufacturer is corrupt ( or someone has gotten good at counterfeiting their certs and security) .
The SPOT PRICE , loosely applied, is the going rate for a commodity. However, you will find the actual price varies by the form of the instrument, and the specific product you are after.
Numismatic Bullion has a "collector value" - something about its shape, history, origin gives it values above its physical content or melt value. Rare coins, bars from a certain historical mine or mint, etc will have Numismatic value and vendors will charge a premium over and above the spot for them. "Junk" Bullion has no Numismatic collector value - but you will still usually be asked to pay a premium over spot - Numismatic coins will vary more in value and have a greater potential upside. . . providing there is the right buyer willing to pay for that particular coin or ingot.
Junk bullion is usually preferred by the prepper. Old US coins before 1964 are made of coin silver - 90% pure. They are easily identifiable and come in small values that will be appropriate for trading for things like eggs and bread. They have no Numismatic value - they are so many of them no one collects them as "rare"
Junk Gold is really jewelry. In Argentina pure gold bars were sold for "junk gold" prices there being no really adequate way to determine they were pure. As such, a 10-18K gold chain may be a better investment for a prepper. Individual links can also be removed and sold individually allowing smaller purchases to be made.
I personally have used APMEX.com for my purchases which I then lost while fishing. . APMEX is NOT the cheapest. They are, however, in most circumstances, reliable. At least I have had no complaints, nor have I really ever heard of any.