This answer varies. The best advice I can give you is an example. Suppose you need to predict the churn rate of people from X product. You need to have the data on who bought that product, where they signed up, what ads they have seen, what platforms were used, where they are located… to just name a few useful pockets of information.
If you don’t have information gathering set up, don’t worry. A smaller project to ensure you are collecting the right data may slow you down in the short term, but the long-term benefits will significantly outweigh the downsides. Remember, the tortoise won the race, not the hare.