For the bitcoin, you can just invest a certain amount of money every months. The price will rise in the long term.
That's sounds doable for an average investor, the good thing with bitcoin is that we do not need to raise a big amount of money because we can be eligible for investment, a little amount is already enough and we can do that on a installment basis which I believe would be easier for everyone.
bitcoin is rarely rising in long term but as far as i know bitcoin price are more often rising in just short term. the latest price rising also just happen in few days or weeks. these sign mean that bitcoin is definitely not for long term investment. even investing some money every months will be helping you to have some profit out of it