Most importantly, Bitcoin and all other cryptocurrencies are high risk investments that are very volatile. What this means is you should not invest unless you can afford to lose whatever money you put in to them.
It is important to do your own research about securing your money. Learn how to set up a secure "wallet" for any currency you trade, know what the public and private keys are and how to use them.
Information about the historic value of Bitcoin and other cryptocurrencies can be found by visiting http://www.coinmarketcap.com. Because cryptocurrency is a unique product as investments go, people use different perspectives to estimate growth/predict loss. I tend to go by a 3 month straight line tangent.
My best advice is to look for coins that show growth potential, buy when they start to climb and sell either at the highest comfort point for you or when they just begin to fall. This kind of investing requires diligent attention to the market.
If you are looking for good buy and HOLD investments, consider ADA, XMR, and STEEM as your starting points.
Thanks for your opinion man... :-)