A good Altcoin for investment in 2018 is Ethereum.
Within a period of one year, chances are you will get a considerable profit from the investment results Ethereum.
There may be a lot of good coins but I suggest you choose Ethereum because Ethereum uses the concept of smart contract, and this concept is that many people are interested in.
Many coins offer smart contracts.
Ether gained lots of value mostly due to ICOs/ERC20 tokens that people bid for with Ether.
I think the hype around ICO is slowing down. People lost too much money.
BTC is the best choice long term as store of value against fiat.