Difficult question to answer as containment covers a huge range of options. As a trainee I'd look at the basics: reasonably big (maybe 6.5mm) flat head screwdriver, PZ2 screwdriver, grips, hacksaw, file (not too fine), magnetic torpedo level, spanners in 8, 10, 11, 13 & 17mm, square (rafter squares are great) & pencil/marker. Ask your what they'll expect you to bring, but the list shouldn't include anything major.
Containment could be conduit, tray, trunking or ladder. Tray might be mounted on stand offs, but often will be suspended with strut and rod, as will trunking and ladder. There are numerous ways in which containment is put together and supported, from nuts and bolts to all manner of clips and mountings intended to reduce labour costs. The basics are fairly straightforward, but the installation options are too numerous to count.
Tools used on site could include conduit bender, stocks and dies in 20, 25 (less commonly) 32mm, cold cut circular saw (bench & cordless), strut cutter, rod cutter, laser level, jigsaw, grinder, bandsaw, SDS drill, impact drivers/wrenches and drills. Usually installations will be to a spec which must be rigidly adhered to, in order to not obstrut other services and deviations from spec 'should' be torn down and reinstalled (I say 'should' as not all sites are created equal). On the other hand, it's not uncommon to turn up to a small site and figure things out as you go - ultimately the aim is support and containment of cables between A and B, with stops at C, D, E, F etc along the way.
Cut resistant gloves are essential as there are going to be a lot of very sharp edges. Safety glasses are another essential item, with goggles being a good idea where grinders (if permitted) and certain circular saws are concerned.
Main thing is to learn and enjoy the work.