Well as most suggested above was bitcoin but for me, those top 5 coins in coinmarketcap have potential on investing and they are trusted enough when it comes to investing and holding it in a long term. I will allocate big amount on bitcoin if I were you OP and the rest of it is on altcoins which is belongs to the top 5 in the market. Always have DYOR in every investment especially new projects that made by the hype, soon they will collapse and will perhaps have a huge decrease in the future, they are good only for a short term like days or weeks.