How can I transition from the Gold Card to the EB-5 visa?

The EB-5 is much more reliable and already with regulations. I would recommend that one first, so you have a safety if the Gold Card is thrown out by the courts, which is quite likely in my opinion.

The Gold Card and EB-5 are two different schemes, the latter being a visa backed by a statute and the former solely an idea in a Presidential Proclamation that has no legislative backing. While forms and a website have been created for the Gold Card, it may be judicially blocked since it is not legislatively enacted.

The Gold Card program is just starting, so one cannot know yet how it will work out. It will require a one million dollar gift to the U.S., so, unlike the EB5 program, the money will be lost, not invested.
If the Gold Card program works, then there should be no reason to transition to EB5. The gold card should provide a much faster method to get permanent resident status than the EB5 program.

Hard to say how long you may be waiting, but as with other green card options, two immigrant visa petitions may be pending at the same time, with the one approved first and with the green card available first continuing while the other is withdrawn. But keep in mind, this will be completely separate processes. The hypothetical gold card gift will not count towards an actual EB-5 investment.

The answer depends on how far you have gotten in your EB-5 process, whether you committed to a project, whether contracts were signed, whether money was wired. Or maybe you went with direct investment route. Please feel free to make an appointment to speak with an attorney.