You might want to start by looking at some of these articles: https://www.smartdogmining.com/notebook/default.html

In particular:
An Introduction to Gravity Concentration
An Introduction to Gravity Separating Equipment
An Introduction to a Dense Media Cyclone Circuit
An Introduction to Dense Media Vessels

Okay, thank you so much.

Do a tracer test to determine your cut-point.

This could be done via a tracer test, using density tracers. The tracers should be selected to bridge the expected cut density and cover the size range treated in the specific plant. Ideally one would want tracers representing the bottom and top sizes to be treated in the plant. Ideally the tracer test should be done under "load", i.e with production feed but this does make the tracer recovery difficult. A second method is to take representative samples of the feed, underflow and overflow and do densimetric analysis on these 3 samples. This will show how the plant is performing.     Thanks Richard

In can also be done using grab samples of the underflow and overflow and measuring the density using density balances such as the Marcy balance.