Soft clutch, no fluid leak/clutch failed

I bought the car nearly a year ago the clutch was soft but shifted good (fastforward) I drive my car to go get fuel get there gas up go to leave and then bam nada the clutch does nothing. what I need to know is how to find out is it's the main clutch assembly (pressure plate throw out bearing etc? Or is it 1 of my cylinders or a blockage in the line?

How do I diagnose the issue so I can repair it?

Also any cheap reliable car parts sites would be appreciated new and used.