For you to start trading you need a source of the bitcoin to trade. You can not just start trading from air and earn bitcoins. I think what OP wanted to know is where people get bitcoin. What people are suggesting here are ways of growing bitcoin but the source of bitcoin.
Hyips and cloud mining will not give you satisfactory results as majority of people have lost their investments in those sites so the best way to grow your bitcoins would be with trading altcoins as altcoin market is full of pumps and dumps so if you choose the right coin at the right time then it can grow your coins in the best possible way.