Different investment strategies require different initial investment levels.
A low risk trend trader might be able to trade with $100.00 using 0.01 lot sizes, even less if it's a cent account.
A high risk coin toss trader who is always in and is using a Martingale gambling strategy to increase the lot size on each new trade, will absolutely need a considerably larger initial investment,
Never trade with money you cannot afford to lose. If losing $1000.00 will cause ANY negative consequences in your life, then perhaps it is unwise to invest $1000.00.
What investment level worked best on your demo account?
Only you can determine what will work best for your trading with a Live account.
If you want to be profitable, make profitable trades.