It is very easy to increase bitcoin, just by it with your cash.
I think he is referring on how to increase btc by means of working with it not just by buying. if you already have capital, better try how to trade but make sure to educate first yourself on how things work. its not going to be easy and also risky but give it a try. if you became a good trader you will earn for sure.
If you already have capital then try to avoid trading ,try to to invest in legit projects.you can also invest in exchange shares though you will get less profit as its long time investment but a safer one.
but i think the best way to make bitcoin is trading. from trading one can get unlimited amount of bitcoin. in trading you even do not need for such a big amount of bitcoin because you can start trading in bitcoin or alt coin with a very very little amount of bitcoin and still have a very good chance to make more money from investing a little amount of bitcoin.