ETH is really good to have whatever you do. When you are not invested in an ICO you can be invested in ETH. Which means that everytime you have money to invest, make sure to buy ETH, in that way you'll have a good currency that will be stable overal and gain you some descent profit over the years. When you find from the other hand a good ICO that you really want to invest in, then you can consider liquidating a small portion of your ETH holdings and invest them in ICO's. That's the best strategy I can think of, in that way you'll make profits form ETH gains and at the same time be able to invest in ICO's in case something really awesome shows up, don't invest in useless ICO's because the majority out there is just that - useless.