You should investigate and find the best ICO that will give you massive return when you invest. Just like stock market, the stocks may increase and gain profit or it may decrease and loose investment.
Even with the non massive investment type is okay. You dont need to risk too much with that massive return that you are saying or you will end up with nothing. That is how it is. High risk, high income. But you can somehow change that.
Invest with small ones but if you can manage to monitor as many as you can then the profit will be the same with the massive return. You just made is safer than just one investment.