There is no one-size-fits-all answer to this question. The amount of data required for the recommendation engine will depend on the type of task you are trying to accomplish, the complexity of the task, and the available resources. In general, however, it is advisable to have as much data as possible when working on deep learning projects, as more data will allow the algorithm to learn and improve its performance.
Our Data Scientists are experienced in providing preliminary Data Quality Audits and in preparing a dedicated data collection strategy for our clients.