There are many altcoins with huge potential. I recommend you to stick yourself with the top 20 altcoins in coinmaketcap list.
I would recommend researching low market coins and ICOs as well. Some of them are going to potentially increase x50 to x10000 like some of the other high market cap coins did. Meanwhile high market cap coins are less likely to see such dramatic returns.
"x50 to x10000" What the hell? I do not think we always have the ICO project can give us this profit. And only the project for long term can do that, it is impossible for short term or mid term investment. Few years is needed.