These are the commonly used pots in my build. When ordering make sure to get the correct values.

These are the jack sockets used in my builds. It's always great to have some spare ones on hand.

To keep the costs down and increase availability i use the regular sized SPDT switches on my builds.

My builds mostly use 0805 LEDs since they give a good and pretty even light source behind the front panel. Choose the color you like the best for your module.

Some builds require little trimmer that are accessible through the front panel. These are the ones used in my builds. 

Some modules need spacers to hold pcbs together. There are affordable sets available that either plastic or metal. Of course the metal ones are much more stable but some might like the black color of the plastic ones better for their builds.

I use these knobs on my builds. I think the silver ones look the best but feel free to experiment with different colors.

I don't use IDC boxed headers one my builds since the simple pin headers tend to be much more affordable.

Capacitors are an essential part of any module. Besides the electrolytic caps you need smaller ceramic ones of size 0603.

Some modules use encoder to select parameters instead of regular pots. Be sure to the the right shaft that fits your knob of choice.

To fix your modules in the rack you need screws. These are available in large quantities relatively cheap. I recommend a length of 5-6mm.

Probably the most frequently used component. I am using 0603 ones on my builds. It is best to get a large book with many different values, then you have everything well organized. Values that you run out you can then simply reorder and refill.

Some modules need vactrols. Feel free to experiment with different types for a slight change in sound.