I say what I did when I selected how to earn bitcoin.

1. I Started with creating wallet and found some fun sites called "faucets", where in form of games you can earn small amount of bitcoins. Time to time there needed to watch advertisement.

2. When i tired watch adverts and got for it a negligible amount of btc, i decide buy videocard that can help me earn more. Actually videocards mine not exactly bitcoin, but another cryptocurrency, what you can exchange. First time i chose old and not very good card, but it was great experience. Next time i buyed videocard with good performance for mining. And i time to time buy more card when i can.

3. First time i get acquainted with exchanges to convert my eth,dcr,zec to btc. Just sold all, did not expect growth. Later i found that some coins greatly increased in price. So i started trading - buy at low and sell later when high enough.

4. Finally I saved up the some money and buy my first ASIC. It works for me almost 2 years now, and his roi more than 100%.

Try it all and you'll find best way to earn bitcoin.