Consider the system's strategy, risk level, and broker's margin requirements. Review past performance and consult your broker for specific deposit guidelines.
This information should be available to you before you sign up with a broker. I would not recommend trading if you not sure what your costs and risk will be....
Personal opinion you should just use the same capital as the system's capital. If you really want to start with less use this formula: Trader's Balance / (lots opened x 100) = Balance you need to open with 0.01