I think the current coin that is very suitable and very good for investment is bitcoin and XRP, you should be able to see the opportunity of XRP price movements that seem to be very expensive by the end of this year.
If you are looking for long term source that will generate huge profit for you then you should go for Bitcoin which is the most profitable and convenient. However it is hard to achieve it I mean to say it is hard for a person with low saving in order to afford Bitcoin due to its high value but currently it is available on low price so you can get benefit of this opportunity is my suggestion and now the decision is yours.
My choice for investment in cryptocurrency is bitcoin and Ripple. Bitcoin is because it is the biggest currency in the world and Ripple is because it is also fast growing crypto and the market cap is also very high and the price is also very low. I can hold big quantity for low investment. The future of Ripple is also very bright because the increasing number of investors.