This is a question that have been asked a thousand time.
If you are a begginer, start with what you can afford to lose. As a pro, I can start and build account from 1k to tens of thousands in days or weeks by step by step strategy, but it involves great dedication and high level of dedication.
Higher deposit makes less brain activities and profits with no much dedication of the entire brains.
But with less deposit, you have to detail and follow up your entry points just to build the account to a better starting balance.
If you invest little and get a lot, then I will be the first to learn from you. In my opinion, the maximum return that can be obtained from classic trading is up to 15% monthly. Don't invest in your account balance, but in your skills.
Depends on your own situation. If you have lots and lots of discretionary funds, how much depends on your mood. But if you don't have that much money, I recommend less than $1000, which is not for making money, but for increasing your trading experience.
It all depends on your experience, having a good strategy that you have tested on a demo account, you can make a deposit of more than a thousand dollars. If you only want to try, then less than a thousand.
Make money with people who know how to make money.