There are about 2500 remedies, or so. More are coming all the time. In clinical practice, you really use about 80 remedies most often--so it is a good idea to keep these very commonly used remedies handy in different potencies, and to have at some fundamental understanding of these remedies so that you can have some ground on which to differentiate between them. Of course, lots of other, less commonly used remedies may be needed too.

However, memorizing the materia medica seems like quite a lot of energy put to poor use, when reference materials are created exactly for the purpose of making that information accessible. The most important thing is to take the case properly and learn how to analyse the case so that you really do understand the patient. Materia medica can be referenced if one's knowledge isn't profound about any particular remedy, and differential diagnosis between remedies can be done just as easily that way as from "memorization".

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...and deliverance has many faces<br />but grace<br />is an aquaintance of mine