Usually, the profitable coins that are just good for short-term investment nowadays are projects without a strong foundation and mostly carried by the hype which is too risky. If you want sure profit, I suggest that you'll focus on well-established coins. Though it will take time for you to gain your target profit, at least you'll have assurance that you won't put your funds in bubble coins.
That's a good piece of advice and I am glad that you know this fact. The point of investing is to earn money.
Currently most of the coins are going down because of the down trend and there are only a limited number of coins making a little positive gains.
Investing in those coins is just like gambling. So it's better to gamble itself than to invest in those coins.
It would be best to either wait for the down trend to over or invest in potential coins like bitcoin and ethereum and other established coins.