Most of them are probably scam but for sure some of them have potential. You can also participate in airdrops, so you can "invest" withot risking your money. I participatet in the Marinecoin Airdrop a few weeks ago and I got 450000 MTC which is now worth about 50 Bucks. Their Airdrop is still going on but they changed it a bit. You can now claim 20000 MTC every day as long as there are MTC left.I am pretty sure that it will become more profitable in the nearer future since it really has potential: a dev-less, community based coin with zero fees. It is time tested, is a machine to machine system and works with artificial intelligence. Can also become great with iot.