One of the maxims of packing lighter is packing less stuff. Stuff you don't take weighs nothing, costs nothing, and takes a smaller, lighter and cheaper pack to carry it.
Clothing usually falls into the over-packed category. It's bulky and can be expensive. A good rule of thumb I like is that you should be able to wear all your clothing at once, as part of a coordinated layering system.
Many ignore extra weight of the pack(s) needed to carry extra gear. Lighter packs can make a difference. Bicycle panniers can get heavy even when empty.
The best rain gear I've ever owned was custom made for me by a hiking buddy out of silnylon. Anorak and pants each weigh about 3 oz and pack the size of a fist.
A few light weight things cost more, notably down. But a good down bag is a lifetime investment. Cuben fiber shelters are another. (I haven't been able to justify that expense yet.)
Some lighter weight gear is simpler, cheaper gear. Like single-wall shelters. Homemade alcohol stoves are better than free--you can take a couple of Pepsi cans out of the waste stream and make something useful out of them. And your stove weighs a few grams. Repurposed one-liter soda bottles do the same thing--carry more for less weight and better than free.
Many do well with stoveless travel, especially on bikes. It's pretty easy to find a cooked meal every day when traveling by road. My stove and cook kit used to take up an entire front pannier.
My big dome tent used to take up the other front pannier. By using a cheaper, lighter tent and simplifying my meals, I was able to both save money and eliminate the mass of the front rack and packs. And the bike handles better and it's easier to bring places I want to go.