Buying BTC should not be considered as a way to make BTC. I mean you will always have the same number of BTC though its value will increase. There is no BTC made in the process. I think OP is interested in free ways to make BTC and I can only think of signature campaigns for this. Here also, only those people should participate who have sufficient time to complete the posting requirements of these campaigns. These campaigns require certain minimum posts and if you fail to do those many pots, all effort will go in vain.