My preferred bike is 22.3lbs out the door and ready to ride. Have a 16lb road bike but multiple rides have shown me that its barely faster so I'll stick with it but will lighten it some.
Carbon bars are a good savings over the gossamer and really good if you have the omega bars. Check out Merlin Cycles for 3t bars. Picked up 3 sets over the last 6 months for 150.00 each. One for mine and the wife's gravel bikes and one for the cross bike. She loves the ergonova and I find the ergoterra to be stiff enough. The third is waiting for the cross bike handlebar tape to wear out but it'll get me to 22lb once I install it, too cheap to just toss good lizardskin tape till I have to.
Cassette can make a big difference especially with an 11-34 cassette, for a nice bike I'd go XTR/Dura Ace depending on desired gear range. I've also got a real nice cassette waiting to replace my chorus (when it wears out) that will take another 150ish grams off, which I will match with a much nicer/lighter chain though I doubt that'll be more then a 20g difference and probably closer to 10g.
Wheels you don't have to go too exotic. I built my bike with White Industry hubs, butted spokes, alloy nipples and velocity aileron rims which came to just over 1600g, wife's was just under 1600 using lighter spokes to match her weight, and in both cases 32 spoke wheels. Switching to 28 spoke would help a touch more. Cost was under 1k for the set. Not as light as going carbon but sweet hubs, and a strong build. For extra weight savings, ditch the tubes all together if its a gravel bike, I still don't like tubeless on road tires.
So wheels, handlebar, and cassette should get you to 500g or a bit more. Saddle is something to look at as they can have a wide weight range. After that you might have to spend big for small gains. For me, after handlebars and cassette, a lighter set of pedals should get me to your weight range which will be fine, the ride I've learned, matters more. If its a real concern leave the saddlebag, computer and ancillaries at home but I like them.