I see and observe recently that many ICOs are below the ICO price when they touch the exchange. Do you think it's a smart step to wait for an exchange and buy the tokens you want?
I suggest you to buy on ICO sale and after sale when their token / coin already listed on exchanges.
I don't think buy the token only in exchange is a smart step as investor, because the ICO maybe won't raised enough funds from the sale.
If that happening, you won't get the chance to buy their token in the exchanges because they failed.