The very simple answer to your question will be “ETHEREUM”.

ETH is being a great coin with its working platform and creation of smart contracts. Smart contracts brings a new renovation in the life of blockchain technology which allows us to create a masternode or a individual minable coin. Eth will be a better source of investment for ever individual who want to make long term investments.

Also the top 200 coins from the coinmarketcap too are profitable and investing in any of them for long term can be profitable.