I think the cheapest altcoin we should invest now is Ripple and Stellar. Ripple ranked 3rd coinmarketcap, it really has potential. Ripple has the advantage that it is accepted by many banks around the world and used. Stellar has a steady growth rate and its prices are rising fast. I believe that this year Stellar will bring a lot of profits to investors. Now the price of these altcoin is very low, this is the time for us to buy.