The trading accounts will have to be in the LLC's name, its not advisable to deposit funds from your personal account because there are anti laundering rules which the brokers have to comply with and they might refuse to deposit those funds to your LLC's account.
Perhaps the only exemption would be when you add funds to the account using a personal credit card, but then the LLC has to reimburse you for that particular credit card expense.
Also, if you use a credit card, some brokers may charge a fee for the transaction and if you later decide to withdraw those funds there are rules which say that withdrawn funds have to go back to the account they came from and there could be complications as the credit card is not in the LLC's name.