The absolute minimum is 150 USDT on your exchange account. However, some strategies trade with a small percentage of their overall big balance (check the strategy balance). You also need to deposit a lot in order to have a 100% copy trading success rate when following them. It’s important because of the exchange rules. If the strategy places 50% of the deposit to one deal, it means that 50% of the investor deposit should go to the copy trading operation. 50% of $10 is only $5 which is below the minimum amount.
Each exchange has a minimum amount to make a deal.
A general rule here would be "the closer your balance to the strategy one is, the higher your copy trading success rate is".