I am holding LTC, ETH, DASH, XMR, ETC, BCN, DOGE, BCC, PPC and EMC
I always invest in coins with high market cap (the first 50 listed in coinmarketcap).
I have earned good profit from these coins. for example I bought 20 LTC at about 80 dollar and I sold them at about 600 dollar.
investing in coins with low market cap is usually risky.
i think Litecoin, ethereum, doge are the most prospectful coins, their price have kept increasing slowly. And most of altcoins must be invested for long time. Because temporary there are too many icos' so the fluctuation is too dramatic. So i suggest just hold till next year and wait for new issue.