What values can/should be used for the isentropic efficiency of a compressor and turbine?
An answer is in the table of the linked question: What is the efficiency of the turbine of a modern jet engine?. Column 4 is for modern engines, column 1 is for old engines, about 1960’s technology. So, take your pick. In order to get a simulation running, an exactly correct figure isn’t necessary, something in the ball-park is fine.

The third comment above gives another similar source. Either would be fine.