‘How many references are needed to make a good literature review?’ There is no straightforward answer to this. In general, an appropriate number of references would be in the range of 15 to 25, with around 20 being typical. However, this is not hard and fast, and will depend on the topic and research question chosen.
The crucial thing is to aim for quality and relevance; there is no credit to be gained from amassing a lengthy list of material, even if it all appears to be relevant. Part of your task is to select a range of references that is appropriate for the length and scope of your research project. It is easier, and more conducive to good research, to handle a smaller number of references specifically chosen to support your argument. Remember also that in general, a student whose research project contained a smaller number of references would generally be expected to demonstrate a deeper and more critical understanding of those references.