If you open an account with any domestic institution or agency, you may be charged the difference plus commission.
The spread of foreign exchange is basically at a low level of 2-5 points, and gold generally only receives 5 points, which is regarded as the normal collection of 10 points.
If you really don't know how to calculate the spread, you can open a simulation account and try to trade several times to know how to calculate your own spread. If you still don't understand anything, ask more people.