You can get rich by using the bitcoin as a long term investment, I think this is the best method to get rich without any big risks.
Its of course always a risk you are taking but you will need to take a minimal risk to gain money and get rich.
How can you say that investing in bitcoin is not a big risk? If you are investing into bitcoins that is the maximum risk you are taking as you don't know how long bitcoin will survive in future.
Yes, investing in bitcoin is something like gambling with your money, either you win or you loose totally depends on the market conditions and especially on your luck.