I prefer buying a coin when it already has a real product and listed in big exchanges. This can make a lower chance to hold a bad coin on the wallet. Also, this can avoid a severe pump of the price after buying the coin. I have some experience buying new coins from small exchanges, I can tell you it is very risky. There are too many new coins that result in a very low volume there. And finally, the price drops significantly because of too low demands.
Defining "real product" is problematic in cryptocurrency sector. I would define a coin or token as a "real product" only if it is having an established real life usage. And such coins are very rare and as per my calculation they number in two digits. Most of the projects have very good ideas. But the problem is with translating these ideas into real products.