There is no definite answer to your question as everyone has different ideas on what makes a good investment. All i can say is to do research and invest in coins in which you see potential, remember just because a coin is feature rich does not mean that it will succeed NXT being a prime example. Personally i am invested heavily in bitcoin, litecoin, peercoin and dogecoin as these tend to follow each other when BTC price increases. They are also some of the oldest altcoins around and have considerable staying power. They are also all in the top ten at coinmarketcap.