i would do rear seats, spare wheel and any subs/amps.

that's all reversible.

Otherwise remove the above, interior trim, heater matrix, AC, any plastic covers, sound deadening, wheel caps, replace front seats with lighter race seats, remove airbags and replace steering wheel, remove rear wiper ...
 
doesnt uprated parts weigh loads more than standard, intercoolers etc, so theres no point unless you guna do it properly
 
well these car weight alot.
for example if i remove my spare wheel from the boot, how kg will it drop by?
 
thining of doing this and getting tyre weld just for another bit gone from the back, trying to not get obsessed tho