Putting all your funds on one card is always a bad idea. Of course there is a chance that you will earn a lot but just the same you can lose a lot too. Even tough, I am a big Ethereum enthusiast, yet I would not put my all money only in one coin. The best option (also from the educational point of view) is to make market research and find a few coins from different groups (like in top 10 / top 50), which you believe have potential and invest in them propotionally. As someone wrote before, diversity is a key here!