Invest in bitcoin mining you can earn a lot but it depend in h/s that also depend in you hardware you buy it a great ways to earn bitcoin also we know that it getting harder to mine because of so many miner's this days but still a great ways.
Yes, there are many miners already and setting up the rig requires technical knowledge. Also, parts and hardware is quite expensive to start in addition that electricity is also expensive. ROI takes several months, long time to wait

I am considering the signature campaigns, social media campaigns, joining the ICO but see to it first if they have many investors and the project is reasonable.Lastly, trading of cryptocurrencies.