First of all , your main investment should be in Bitcoin and then you can focus on altcoins like ETH , Monero , Dash , Crown , Waves and so on but you should understand the project itself before buying into it. Right now , altcoins are very attractive as price because some of them are near all time low.
Bitcoin is one of the best coins so it's more important to hold bitcoin than other altcoins, at least we have 70% investment in bitcoin and the side of altcoin that you believe is the best altcoin at a price that will be higher due to the bullrun.