Trading is a good way. Setup an account on an exchange and buy a little of a cryptocurrency you are interested in. Study the charts and try to buy in a dip of a popular coin. Once you bought a coin, set a sell price a bit higher enough to offset your trading fees and to make a small profit. Rinse and repeat until you grow your stack. Just remember to buy low and sell high. 
i am totally agree with your opinion regarding how to make money in the field of crytocurrencies. In addition, if anyone want to earn free those can join this forum and bounty campaign for that no need to invest for trading.