ETH is probably the most well known altcoin and has potential to be better and better in the future. ICONOMI also has a potential considering right now the price is up to 70k satoshi right now.
Yeah. Ethereum is one of the most strongest altcoins in the market, being second only to Bitcoin. It has risen in price from nearly $15 to $230 in just a few months and I believe that it will continue to rise and become stronger than ever.
With this in mind, you could consider to invest into ETH for the long term and hold your balance until the right moment to sell and obtain profit. Also, Iconomi has been doing great in price, as well as other altcoins within the top 10 market cap ratings.
Dash has risen exponentially in price too from $12 to nearly $120 nowadays. It is also one of the most prominent cryptocurrencies worth investing into to preserve your profits in the future.
Nevertheless, the above cryptocurrencies are great to baghold just in case there's a massive price increase over the next months. You can also be on the hunt for new altcoins that might eventually become valuable in the long term. Just sharing my thoughts.