Here is my comment/advice. You do not mention how much experience you have, so I am going to try flying blind. First, if you don't have much experience, the truth is that getting it is going to cost you money. The least painful loss is to lose Monopoly money. You can "play trade" with play cash on a few different websites. This is the best, yet most often ignored advice out there. Second, my advice on the minimum cash to start with is $5,000 minimum. This way, you can invest part in stocks and keep some cash set back for bargain days like today (the market had a ~300 point drop).
Whatever starting amount you decide is right, you can test out your decision with paper money to see just how right you are without wasting your hard earned cash. If it turns out you are wrong on the initial amount, no harm done. Adjust your amount and try again.