My rig is kicking around here somewhere, I just got a sheet of MDF (6mm iirc), as for stuff to put on it I've done a mix of scrounging (old DNO head, DOL starter) and purchasing (sundries like cable, backboxes, faceplates etc and then just copied layout diagrams found online; '2391 test rig' will bring back a few, then I just picked one and cracked on.
I did my rig for the same purpose; terminations and building muscle memory, I don't use it as much now but every now and then I'll get the urge, strip it off, give myself a spec and have at it, you'll want either some reels of scrap cable or resistors to add some 'length' to your cable readings (to better simulate lengths found in houses etc (and not just the ~60cm lengths used in college on the pratical boards.
From memory I had on mine;
One way lighting
Two way lighting
Fan isolator
Shower (realistically a bit of 10mm to a pull cord)
Hob/Oven (bit of 10mm to a cheese wedge
Ring socket circuit
Spur socket from said ring
Spur FCU from ring (then onto a lighting circuit - a garage feed in essence)
Radial circuit
A DOL starter to a 60309 socket
90° PVC
50mm bubble set in steel conduit - I had got myself a conduit bender for the sole purpose of honing my conduit bending, still use it now and again
Trunking/tray yet to be added.
Exactly what you put on yours is down to you and you don't have to have everything, all at once or at all, it's down to you and how you intend to utilise it.
Do not feel that you NEED to have it hooked up and powered for your purposes, realistically you can do everything at your level on a rig with no power.
You could add a bank of switchable faults but that's getting ahead of ourselves....
Bit of MDF, scroung any wiring, accessories etc [used/aged] stuff will add an element of authenticity
and an idea of what you want your rig to do for you.