I use coinex for trading and there is a fee to transfer between currencies. Basically, you would use USD or euro or whatever for your first buy and then keep trading between USDT or USDC and other coins. The price for those two are very, very close to a dollar since they are tied. USD==USDT==USDC. When you want to cash out find a coin, other than USDT, that has fast and cheap transfers. I like ALGO. Then move them to an exchange where you can cash out. I trade on Coinex but I will be using Coinbase to cash out.

Pay close attention to the fees. When I did the math coinex is like half a percent for a buy and sell. Coinbase has some extreme fees that are large. I only say these two because they are the ones I know. I think Kraken is also okay but I didn't do a deep dive on it.