Hello,
Please answer this question:
"I visited
https://etherscan.io/gastracker and it shows me that the current Ethereum gas fee is "$13.XX", then its mean that if I want to swap some Ethereum based tokens, then I must have "$13.XX" Ethereum in my wallet? Any amount that I swapped or transferred, just cost "$13.XX"?"
Yes, you must have a maximum payable gas limit for the activities you do. If you want to make transactions in large quantities, $13,XX gas fee are still within reach. But if the transaction is small, you can wait for cheap gas fee. Usually when the gas fee is cheap, transaction become slow because miners will prioritize transactions with higher fee.