Silver coins are minted in meany denominations and in many countries. Collection for investment and collection in historic value are two diffrent catigories.
You should first understand the content and differences in the coins.
The Modern America Double Eagle is for the most part considered Round Bullion. It is 999. fine silver and costs spot plus premium. These numbers change daily but chances are as a ball park number you'll pay spot plus 2-7 dollars, per troy ounce.
These rounds should be kept in plastic sheaths to keep them from becoming worn or damaged.
The Morgan and Peace Dollars are largely collected for their Historic Value and contain 90% silver. Obviously uncirculated is the best investment. Carson City mints are bay far the most Valued but there were fewer minted. Focusing on this one key word -fewer- is where collector or historic value is important. You can run these coin dates and mints on a website called CoinTrackers. Common dates are concidered junk silver and are worth 10-18 times face value depenting on silver spot. Likewise American coin 1964 and earlier are 90% silver. I always check my change before I spend it.
The Chinese Panda is concidered the best value, it's 999.9 fine silver, and years very in values, and do not fluxuate as the silver market does. The other really fun thing is the Panda reverse changes eary year, it a lot like investing art and not just coins.
Canadian Maple leafs are also 999.9 - they buy and sell like American Bullion rounds. Although candia currancy is partly silver. Silver trackers will tell which years have significant amounts of silver.
Definately check out the Pandas.