First rule, DON'T keep any coins on centralized exchanges, or be ready to accept the risk and lose everything in event of next hack that is ready to happen.
You are not a trader and you don't have a clue what you are doing, so it makes it even worse.
So I'm wondering what the cheapest way would be for me to send money to each of these exchanges?
You don't need to use five exchanges for this, and you don't need to complicate things when you already know what fees they charge.
Going for cheapest option is not always the best and I don't understand why would you send fiat money there and exchange it with fake fiat like USDT that is much more risky.
Just upload an amount via credit card or bank transfer to each of these exchanges?
Credit cards have highest fees for sending to exchanges so you can eliminate this option.
Bank transfers usually have less fees than credit cards.
Should I upload the total amount to one exchange, and then transfer from that exchange to all the other exchanges, and bear the network fee?
Depending on coins and network you are using, you will have to pay withdrawal fees that can be very high sometimes, so it's double waste of money if you do this.
Any idea as to the best and cheapest route to take?
I will say this for the last time and I will not repeat.
Buy directly using p2p trading, pay with cash or use decentralized exchange Bisq.