What did you start out, with, what did you cut out along the way and why?
Oh god, where to begin.
First, you can lose pack weight multiple ways but ultimately there will be times when money becomes an option because ultralight gear can be expensive.
I started with an REI pack and then went to a GoLite Pinnacle and ended with an Osprey Exos. Only buy Osprey.
I started with a Marmot Home Alone Bivy and switched to a Big Agnes Fly Creek UL1. Most people like the UL2 more than the UL1. It's a preference.
I cut out luxury items (utensils, knives, cup, nalgene bottle, solar panel, etc.)
I switched from a Mountain Hardware ultralamina 45 (synthetic) to Western Mountaineering Highlite (down) (single greatest sleeping bag in the history of man). I also own a Western Mountaineering Versalite for cold temperatures. The best sleeping bags are Western Mountaineering; although the new Marmot Plasma is pretty rad.
Find multiple uses for everything you own. Example: If you have an extra pair of socks then use one as a sunglasses case and one as a camera cover and then you have two less things you need to carry.
I started with MRE's and grocery store food. I then switched to a stove and dehydrated food. Though I had to add a stove and fuel I still saved weight by not carrying heavy foods because dehydrated food (oatmeal, ramen, pasta, mountainhouse, etc.) is so light. I used the Jetboil Sol Ti.
Bring iodine for emergencies but don't use it everyday! Big mistake. I used a platypus 3 liter and added an inline filter so the water was treated as I sucked through the hose. To clean water for cooking I just boiled instead of treated.
Started with a Thermarest prolite and ended with the Thermarest neoair. Nothing tops a Neoair.
Also, you'll gain knowledge about gear as you go. For example, down fill power. 600? 900? These numbers refer to "fill power". Fill power is a measurement of the loft or "fluffiness" of a down product. It measures the volume in cubic inches displaced by 1 oz. of down. It's important in sleeping bags and clothing made with a higher fill power down because they have more loft and trap more air. So, to achieve the same temperature rating/insulation, less of this down is needed. This means a better quality sleeping bag will be lighter and more compressible. Most high quality bags will have fill powers of 600-650 and superior bags will have fill powers of 800-900. Higher quality down (800-900) occurs when geese molt in spring, leaving clusters of down. This down has very few feathers and also has more oil on it. These clusters not only loft higher but are more durable. It is more expensive initially, but over the life of a bag it will save you money. Remember that the sleeping bag should be unrolled & fluffed first thing when you get to camp and lastly when packing up camp. The less time the bag is compressed the better for the down. I keep my sleeping pads inflated under my bed 365 days a year and my sleeping bags on hangers in my closet 365. Don't keep them rolled up. There's also the synthetic vs. down debate. Down insulation is lighter and more compressible, more durable, will be a better cost value over the life of the bag, more comfortable over a broader range of temperatures, and is a natural fiber. Synthetic insulation stays warmer than down when wet and dries more quickly, initial cost is less expensive, and some people are allergic to down. NEVER let a down bag or jacket get wet. If you're sleeping under an open air tarp beware of down bags getting wet!
Also, if you have any specific questions about hiking or gear feel free to ask. I can talk gear all day but I'd rather talk about gear piece by piece to describe why I chose something instead of making a tedious list.