This is not actually a good idea. If you invest in just one altcoin and down down trend strikes again, all prices falls down what will gonna happened to your only investment? But if you divide your money in different promising coins, there are still 50% chances that you will gain your profit for the recovery period because all of those coins will recover more profit loss than only one altcoin.
in any case, the capital that you want to invest is better divided into several areas, rather than focusing on one or two projects. This minimizes the risk of loss and increases actual income in the future.