If you want a real mining then I think the better way is to use a real mining device like laptop and pc cause using android for that doesnt really works.
If you're talking about mining Bitcoin or any other major cryptocurrency, then even using PCs, even dozens of them, is going to be a waste of time and energy.
To make any real profit, you would need to invest in proper mining hardware.
The problem with cloud mining is that most of the services out there are scams.
I believe what the OP is asking about, and what his friends are probably using, are those walk-and-earn apps, which most of them turn out to be scams as well.