Being somewhat next in line to you at starting up on going light to UL to SUL, I would offer the following advice (with the caveat that half the fun or more, and in fact a necessity, is that you find the right gear at the right price for you). That said here are a few things I learned in the last year.
Number one, on thinking about it, has to be shoes / boots and sock combinations to keep your feet happy. That, aside from hand / glove / mitten fixtures for extreme cold may be the most important issue that I lucked out on. Because I went to a good and sometimes pricey mountaineering shop I got fit with both a pair of low tops and mid tops that fit beautifully and were extremely comfortable. That meant walking was no longer a "macho" sport event. I happen to like the mid top Tecnicas that I got with expedition weight merino wool Patagonia socks. It is so easy to walk in. But, to really get lighter I took a leap of faith and went low top with some Montrails and lighter socks, and it was also extremely comfortable at much less weight. I still go between the two, but I am forcing myself out of the habit of taking the heavier gear -- it is psychological for me, security v. the unknown. Couldn't be happier than with the advice gleaned here at BPL.
Second, the sleeping bag I chose after looking at a bunch, was the Mountain Hardwear Phantom 32 F at 1 lb. 5 oz. Now there are many good and wonderful bags at less weight and even lower temp ratings, but because I was transitioning I bought the Phantom at REI, who guaranteed me they would take it back if I was unhappy after testing it -- imagine that.
Third, the pack had to be resolved and again I bought an REI UL 45 and an Atmos 50 to try. I never quit using the REI because it worked for me, I needed the framing for my back but it weighs 2 lbs. 8-10 oz. without cutting junk off. It works, got and kept me out there so it is still my go to pack. I also ordered and then returned a lot of frameless packs but was not ready for them. You need to get your feet ankles and body ready for UL gear if you are not in the younger flexible body group. But, it does happen over time -- so now I am waiting to try the Whisperlite at 3 oz. or so.
Fourth, the cooking system can be whatever you want. My go to stove is a SnowPeak Giga with a small cannister, supplemented now with esbit tab light weight stove from the BPL gear shop and a woodburning Bushbuddy for the season when you can have fires.
Carrying too much food is something the sage ones here all talk about. It is a mental disorder of our society. I have still never carried too much food, even though I feared starvation and death looking at the few granola bars and small sack of food I was going to carry. Ditto for too much water, in my case. I learned to carry a .5 L Platypus after checking on the availability of streams and lakes or snow. Also, out of safety I carried a Katydyn ProHiker, went back to a Timberline and am now going to work on using aquamira. That cuts lots of pounds, not just ounces, out of a pack weight.
Clothing is again, like shoes, really personal and took another gradual trust building series of tests -- but "Dr.J" pj and all the others are right on. Food and clothing are expendable items if you pick the right base, mid, and shell layers.
It takes a long time to even begin to get a basic go to system put together, for a tent I go to the Squall Classic or an old MH Tri-Lite 2 w/o the fly in good weather. I am now working with tarps and trying to learn to pitch them, otherwise I use a Tarptent when my partner doesn't insist on the Tri-Lite. Bivy's is a whole nother world and fun.
But, not to go on forever, it is fun to see someone going through the process -- it is entirely enjoyable if you don't make a mistake in shoes and socks, or underdress for cold, or don't take some kind of wet weather gear and get rained on. for some reason, I don't think anybody carries too little food or water, so I wouldn't worry about that unless it was water in a desert or long trek without a lake or stream. Bottom line: the people here at BPL are right on and aren't messing around with newbies, like me. And, they even make their own gear which I wish I had time to do. Anyway, that is kind of where I am at and what I have done being in line with you. bd