-You can start investing bitcoin by buying some bitcoins. hold them for a couple of months and sell them when you think you gain profit of your investments. there's a lot of way to invest that would give a profit aside from holding BTC. one example of this is Mining/Cloud mining, you can enroll into several trusted site to invest your btc in mining platform and you will earn profit based on the platform of investment you choose.

-Its always better to do a research before you make a move to invest and trust any investment sites. there are a lot of legit sites and there are also many  scam sites just carefully analyze them base on the reviews and testimonies of current/previous investors.