+1 new tires (some type of schwalbe) also, the high end schwalbe tubes can shave 100gr/pr from other options.

maybe go 1x up front (depends on your hill conditions and the range you have on the cassette).

a new saddle could be found that is lighter and equally/more comfortable for not too much.

carbon seatposts can be had off ebay inexpensively.

new brakes + pads, also. not pricey. weigh much less and will offer better stopping power. (v-brakes).

first, lose the pie plate, then tires, then brakes.