To buy silver at a low price, check whom the purchase will be made from and if they're reputable. Make sure to purchase silver valued by weight rather than collector's demand as is found in rare coins. Also, know what type of silver is desired and try to buy in bulk.
Buying silver from a reputable dealer is important due to the fact that they will be providing actual silver and not other metals that are just coated in silver. Buying fake silver will only cost money and there would be no return upon selling it.
Developing a relationship with a dealer will promise good "over spot" price. This means the price the dealer is selling it at compared to the price of raw silver. Every piece of silver bought from a dealer will be over spot due to the dealer needing to make money. However, developing a relationship would bring a better price overall.
Silver needs to be bought based on its weight and not because of how valuable someone may say it is. While collector's edition coins may be worth money because they are rare, it all depends on the market for them. Buying silver based only on weight will save money because it is purchasing the silver based on its future worth as a whole.