What would be the best way to earn BTC aside from faucets, signature campaign, mining or buying it?
You can go for altcoin trading or investing in ICO as both this methods are very popular at a moment and majority of people are investing their money in it and making really good profits out of it as if you invest in right ICO then your profits may exceed even more then triple of your investments depending on the success of ICO.
Investing in ICO now is not that profitable like before, that is because there's a big competition already.
I think the easy way be profitable now is to trade, look for an undervalued coins and wait for the big news and buy it as it's expected it will pump.