I do not know what people prefer however I would invest in some such as, Litecoin, Ethereum, Dash Coin, Monero, Waves, Zec, Doge and Byte Coin. They are coins that I have been following for a long time and always have variations of values ​​up doing so that I make a profit when they go up the value.
But there are several currencies on the market today, so research calmly before you go shopping. Try to see currency price histories to see if you can profit or lose money.
Watch out for ICOs see the project well because several of these coins are being used for SCAM and to take money from your investors.