I have invested in 3 coins
1) DAS <--- dead now i think
2) Eternity
3) Arctic Coin
2 and 3 have lost value over time so what i learn is...that MN coins can easily lose value. Be careful what you invest in.
You can also wait for eth pos system and it will be the biggest in the world. They are getting casper upgrade and then pos system will be presented to the community. I strongly recommend eth pos system if you can afford.