Can I skip the TX in order to win more serial ports?
No? Without a TX you can not send data to your DFPlayer which I thought was the whole point.
Can you please suggest a way how to create new serial port?
Yes use something like:-
SoftwareSerial mySoftwareSerial(10, 11);
That creates a second serial port, you already have one real serial port on your Arduino Uno.
Note with software serial you can have as many instances as you want but only receive on one port at a time, which will not be an issue with what you want to do.