The answer to that question may be more complicated than one hopes. In most cases, it is better to participate in an IEO and sell afterward than invest after the IEO. But that doesn't happen all the time. Take a look at Binance Coin and you see what I mean. Bottom line is, one needs to do a complete background check of the product before investing.
Binance coin was one of the successful listings. But there are hundreds of failed listings out there. Theoretically, you can say that investments should be made after proper research. But from what I have seen during my association with cryptocurrency, there is no guarantee of success even if the team is good and the project is 100% perfect. The cryptocurrency market is extremely unpredictable. Shitcoins may get huge spikes, and good ones may fail to get any investment or interest from the whales.