mine sounds so frugal next to this lot - but I've used it for 20 years .... it's grown over the years ... but not much
it depends what he's going to be doing - day to day at the moment I use two screwdrivers a combination plier set (leatherman style) which cost �4.99 from a BP garage
and a good pair of needle nosed pliers.
the rest is bodging stuff. tape, glue, ties etc
probably about �40s worth if that
I also carry one of these for rescuing HDDs
http://www.maplin.co.uk/Module.aspx?ModuleNo=4 8965&doy=27m9&C=SO&U=strat15
one of these for testing power units
http://www.maplin.co.uk/Module.aspx?ModuleNo=4 8647
I still have a multimeter - but many don't
but also a range of long 'uns short 'uns phillips, torx, in every size - collected over years
cable ties, tape, araldite and super glue neoprine tape double sided tape - never throw a screw away
and a utility disc I've compiled over time - which never leaves my side (actually it's a lot of CDs - every diver I've used over the years .... every operating system from dos 3.2)
much of it you can't buy over the counter.
I'd say ... don't go overboard - I carry a bag not much bigger than a pencil case ... the rest is available .... but rarely used .... most faults are software ... the hardware stuff rarely needs more than a single screwdriver
much more fun to pick up what you need as you go (B&Q, maplins ... motorway services, petrol stations ....
builders need far more stuff than techies