Maddy, The whole UL style is a world in itself, and there seems to be no shortage of gear aimed at lowering your base weight.
If you are serious about light and fast, you need to start looking at the UL sites like
www.backpacking.net aka The Lightweight Backpacker (which I have belonged to for years and help moderate) or
www.backpackinglight.com, which is partially free and partially subscribers only. There are many others, but these two are probably the best.
Start reading the UL books like the ones by Andrew Skurka or Ray Jardine.
I am not a UL hiker, I usually go in winter alone and tow a sled, but after belonging to TLB for years, I am familiar with a lot of UL gear:
1. Start with a UL pack, GoLite makes some good ones, so does ULA and a few other small companies. They come in various sizes;
2. Shelter-use a UL tent like a Tarptent, Big Sky or Lightheart or one of the many sil-nylon tarps. There are other companies making UL tents, including winter tents from Hilleberg and Terra Nova, among others;
3. Cook kits and stoves-alcohol stoves (usually homemade) with cookkits made from things like Heineken cans. Jason Klass has a lot of stuff on his websites about making these things; lots of other sites do too, find them with Google; Plenty of videos on YouTube.
4. There are UL pads of all sorts, they tend to be narrow and some people only use a half length pad.
5. Water bottles-as already mentioned, plastic water bottles of various sizes are common-far less weight than a bladder or Nalgene;
6. Trail shoes instead of boots;
9. UL sleeping bag-pricey but light down bags from Feathered Friends or Western Mountaineering or get a quilt kit from Ray Jardine, the original, more or less, UL proponent;
10. Filter-forget the filter and use chlorine dioxide water purification tabs like Aquamira.
11. If you are a hammock person, there are hammock websites with plenty of info on them for all seasons. Videos on YouTube as well. The videos by a guy named Shug Emery are informative and funny.
12. Food-make your own freeze dried or dehydrated meals; there are quite a few websites with recipes for things like freezerbag cooking and making things like stew, then dehydrating them for packing.