I would say the best method to grow your Bitcoin would be using your BTC to start a gambling site, since 50% of Bitcoins economy is gambling...it would definitely profit you.
But you also need a large amount of btc's to be invested as no player will play in a gambling site if the site has less bankroll.
You also need a team here includes coders, developers, support team etc. which are also part of your financial expenses regularly together with promoting, advertising, hostname etc.
There's a hidden expenses to so watch out.
Yes maintaining a gambling site is not that much easier and cheaper. Once he got everything set up and running live, you need to start a new thing, called advertising of your new gambling site. Many people are doing this by signature campaign which would cost them around 2 bitcoins every week.