Top 3 altcoin that I recommend you buy is Ethereum, Cardano and NEO. They are valuable and potential altcoin, they are highly appreciated by many experts. Ethereum is the queen of the market, for me Ethereum is always worth investing. Cardano has a professional team, it has very good scalability, I believe in the future this will be a great rival of Ethereum. NEO is called the dragon of Asia, it has a very large community, compared to Ethereum, NEO has faster transaction processing. NEO really worth to invest.