wait from start to buy at a low price after the price rises then we sell it at multiple prices and the result we earn several times the profit if it can be called by gambling?
Are you describing trading that way? Have you heard that trading can be also a sort of gambling? I understand what you are trying to say but you're going far from what the topic we're discussing here.
There's risk and when there's one involve you have no assurance that you can do it several times but it depends on what are you implying with buying and selling. Not all the time you're in good prices to sell and there are buyers that will buy what you sell with higher price.