the best way I think to increase the amount of bitcoin we have is to invest in ICO ato trading bitcoin or alcoint, if you want a safe then simply hold at a certain time it will benefit.
Nope, that isn't the best way according to my experiences, do you know on 100 people who invested only 30 people make profits with it and the rest are loss? Specially it's a crypto market ( the biggest fluctuation market ) . Yes you earned profits from it but you could lose them all at anytime.
But if you keep it without trading or investing in ICO's you'll never grow the BTC amount in your wallet. Crypto is all about high risks, everyone knows it. So, you definitely should invest in ICO and learn how to trade...or you have any other ideas?