Before investing, make a thorough investigation in the coin you are investing in and do observe the coin's statistics for atleast one year. Also, try investing in the top 10 coins as they are the least risky coins and are no longer considered under a financial bubble which can burst.
You can consider Ethereum, Bitcoin, Litecoin for your portfolio as these coins are well accepted in the financial market and have great prospects for the future.
Its true that we should make investigation or research before we make investment in some of coin. Invest on big liquidity coin is one safest way because have big transaction in market. But i think, the best crypto is bitcoin, ethereum because both coin dominating more than 60% market cap value