A case is needed to house and power eurorack modules (see here for a very big list of existing eurorack modules)
A case consists of one or more rows (each 3 Rack Units (U) high) with a certain width (measured in Horizontal Pitch (HP).
There are cases commercially available with the cheapest (only 32HP wide) one starting at 85 Euros. The cheapest case with two 84HP rows costs 300 Euros. That means building your own case is the cheapest option unless you are ok with a tiny case. See here for commercially available cases.
Note: It would generally be clever to collaborate and communicate with collegues to split shipping cost (Reichelt for example is 5,60 Euros) or to split parts (like the 100 piece bag of M4 screws).
The powersupply is necessary to generate the right voltages (+12V, -12V and 5V) from the 230V AC in the power grid (read up the Basics in our Powersupply Wiki Article).
Our research showed that the cheapest safe way to get such a supply is the 65 Watt Meanwell RT-65B found at reichelt for 25,35 Euros (pictured above).
The job of the busboard is to distribute the voltages generated by the powersupply to the individual modules (read up the Basics in our Powersupply Wiki Article).
You need one busboard for each row of your case. One row needs one busboard, two rows need two busboards, three rows three and so on.
There are multiple options to get busboards, these are the cheapest options:
The cheapest option per busboard is a busboard DIY-Kit at Clicks & Clocks for 22 Euros. These are however not easy to solder because the huge copper traces suck the heat in. With a good soldering station it is managable (ask @dh ) He also sells assembled busboards for 28,50 Euros. Clicks & Clocks is a small shop in Berlin and you will need to write a mail to order.
Your modules will be mounted onto standardized rails which are 3U (~133mm) apart. The rails will be screwed into the wooden case on the sides.
For the rails you will need three things (again the cheapest options we found):
Rails ("trägerprofil") found at reichelt for 6,99 Euros per piece. You will need two per row! The rails are 431,8 mm or 85HP long.
Within these rails you will need a threaded rod to screw in your modules. The cheapest option here is a pack of four found at reichelt. You will again need two per row. So maybe you could organize to buy one of those packs together if only one row is desired. The threads are M2.5
Screws with M2.5 and 10mm length to mount the individual modules. Note that many modules come with screws themselves those are however M3 and not M2,5! Reichelt sells a pack with 200 pieces for 2,55 Euros. If you are sure you will need less than 200 you could split these with a colleague.
Screws to mount your rails to your case. You will need 2 screws per rail (or 4 screws per row). Use stainless steel M4 with 35mm length (stainless steel because they will potentially need to cut their own thread). A pack of 100 pieces costs 9,95 at reichelt, so maybe one pack is enough for the whole course?
You will need something to connect your powersupply to the electrical grid. Ideally you use a noise filtering "Kaltgerätebuchse" to reduce hum.
The cheapest version is this noise filtering plug at pollin for 1,95 Euros.
Additionally you will need a Kaltgerätekabel/powerchord which you probably have lying around – these are very common and look like this:
To avoid hum and ripple on the powersupply it makes sense to load it with something which has a growing resistance with a rising temperature. Oldschool tungsten light bulbs proofed to work here (and as a sight effect you have a light inside your case). The bulb costs 0,50 Euros at reichelt and the fitting E10 socket costs 0,31 Euros.
Ideally you get more than one bulb per person, so you have spare ones in case it breaks (try buying a E10 6V bulb in stress on the evening of your gig – you will fail).
Warning: if you have no experience with electricity do not do stupid stuff on your own, ask professionals!
To connect your powerplug to the powersupply you will need 3 wires (dangerous 230V AC, Neutral (but still dangerous!) and protective earth (PE). On one side of the wire you need to add a isolated flat connector sleve ("Flachsteckerhülse"). The other ends can be drilled and fixed to the powersupply. Ideally you get those flat connector sleves in three different colors (e.g red, blue, yellow) so you know what cable is what and avoid dying of young age. The wires can be recycled from scrap wires at Computerei.
The powersupply takes the 230V AC from the powergrid and converts this deadly voltage down to 4 voltage levels by dark magic. These resulting voltage levels are all DC: +12V, -12V, 5V, and Ground/0V. Ideally you would like to have a star topology which means: everything that is connected to each of these voltages meets at one point. This point are usually the powersupplys outlets.
You need two cables from powersupply to the bulb's socket (one from GND and one from 5V). One side drilled, one with flat socket connectors.
The next connection between powersupply and busboards. Four wires each from the powersupply to each busboard/row (+12V, -12V, Ground/0V and 5V). One side drilled, one with flat socket connectors.