I'd reduce unsprung weight before I bothered with everything else. I haven't even touched the unsprung weight yet. I can't justify spending $800 on the wheels I want, and I haven't been able to find them used. Plus, I already have alloy wheels. If I were running steel, that might give me the extra push to buy some lighter ones.
I remove any heavy objects that I don't need in the car, but I don't give much effort to reducing weight since it doesn't make a noticeable impact on FE. The spare tire will stay; I've probably used them a dozen times in my 14 years driving. Jumper cables and tow straps are more to help others, which I've done many times. Those will stay. An Ultimate Frisbee and some golf discs will stay; they don't take up much room or weight, and you never know when you might get a chance to toss the 'bee.
There was a
thread on an Acura forum where a guy went nuts removing everything he possibly could to reduce weight. Stripped the interior, removed the back seats, drove with half a tank of fuel, and even ordered brand new tires and had the tread shaved 50% just to save weight. He did it to experience the performance of the lightweight vehicle, not to save fuel. He'd have been better off buying a Lotus Elise.