A project of this sort must be built in a modular form. This means that you should build each of those circuits separately and test each one in turn. Each one that you build becomes your test equipment for the next one. So, for example, you would first build the audio amp, partly because it is the easiest, but also because it becomes your test equipment for checking the next stage. Next, you should add the deemphasis network and then check it by using a meter at the output of the audio amp. When this is working ok, then build the discriminator on a separate board and test it. When that is working, then build the limiter and then test it. As you can see, at each step, you will have only one stage that is or is not working correctly so you won't be overwhelmed with many faults or errors at one time.
For each circuit, you will need to research how the circuit works, then design your own in schematic form, then build and test. The circuits should each be built on circuit board, either by cutting a board using a knife, by using a pad-per-hole type and point to point wiring, or by etching a pattern on the board.
You might call this approach "baby steps" but it is by far the most likely to succeed. So, to start with, you need to build an audio amplifier. What are the features and specs for this amplifier?