So it is better to name those CEX to see if one of those fees better my needs, every time that I try to convert Fiat money into BTC I usally lost some 5% percent (Comparing the current market price of BTC againts my Fiat rate change), this may vary depending of the amount of BTC that i am buying. And always moving that BTC to another wallet outside of the exchange (Maybe this is my problem) because if I keep that virtual BTC inside the Exchange i didn't lose that amount.
I wasn't talking about withdrawal fees, only trading fees. All CEX exchangers have Tier's/ VIP's levels mostly depending on traders' volume. You can check all of them yourself, it's not a secret. However, depending on your country, your accounts' maturity, or other variables, fees can also be different. As I see it, the certain thing is that you have to either trade more or move them only at certain (bigger) amounts.